feat: Hardhat Viem usage example. (hashgraph#2556)

* feat: Hardhat Viem usage example.

Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>

* feat: Hardhat Viem usage example - remove keys of unknown origin.

Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>

* feat: Hardhat Viem usage example - remove keys of unknown origin.

Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>

* feat: Hardhat Viem usage example - remove keys of unknown origin.

Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>

* feat: Accept Readme change suggestion.

Co-authored-by: Luis Mastrangelo <acuarica@users.noreply.github.com>
Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>

* feat: Fix paths in Readme.

Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>

* feat: Review requests

Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>

---------

Signed-off-by: Mariusz Jasuwienas <mariusz.jasuwienas@arianelabs.com>
Co-authored-by: Luis Mastrangelo <acuarica@users.noreply.github.com>

tools/hardhat-viem-example/.env.example

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+# For Hedera Testnet
+# The operator private keys start with "0x" and are in hexadecimal format
+# Your testnet account ECDSA hex-encoded private key (Ex: 0xb46751179bc8aa9e129d34463e46cd...)
+TESTNET_OPERATOR_PRIVATE_KEY='TESTNET_OPERATOR_PRIVATE_KEY'
+
+# For Hedera Local Node
+# The operator private keys start with "0x" and are in hexadecimal format
+# Your Hedera Local Node ECDSA account alias private key (Ex: 0x105d050185ccb907fba04dd92d...)
+LOCAL_NODE_OPERATOR_PRIVATE_KEY='LOCAL_NODE_OPERATOR_PRIVATE_KEY'
+# Your Hedera Local Node JSON-RPC endpoint URL (ex: 'http://localhost:7546/')
+LOCAL_NODE_ENDPOINT='http://localhost:7546/'
+
+# For Hedera Previewnet
+# Your previewnet account ECDSA hex-encoded private key (Ex: 0x46751179bc8aa9e129d34463e...)
+PREVIEWNET_OPERATOR_PRIVATE_KEY="YOUR_PREVIEWNET_OPERATOR_PRIVATE_KEY"
+
+# For Hedera Mainnet
+# Your mainnet account ECDSA hex-encoded private key (Ex: 0x46751179bc8aa9e129d34463e...)
+MAINNET_OPERATOR_PRIVATE_KEY="YOUR_MAINNET_OPERATOR_PRIVATE_KEY"
+

tools/hardhat-viem-example/.gitignore

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+node_modules
+.env
+coverage
+coverage.json
+typechain
+typechain-types
+
+# Hardhat files
+cache
+artifacts
+
+.vscode

tools/hardhat-viem-example/README.md

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+# Hedera Hardhat Viem Example Project
+
+This Hedera Hardhat Viem Example Project offers boilerplate code for testing and deploying smart contracts via Hardhat with Viem. It includes configuration for both community-hosted and local ([Hedera Local Node](https://github.com/hashgraph/hedera-local-node)) instances of the [Hedera JSON RPC Relay](https://github.com/hashgraph/hedera-json-rpc-relay). 
+
+:fire: Check out the step-by-step tutorial [here](https://docs.hedera.com/hedera/tutorials/smart-contracts/deploy-a-smart-contract-using-hardhat-and-hedera-json-rpc-relays).
+
+# Viem vs Ethers.js Comparison
+
+This comparison aims to assist developers in selecting the most suitable library for their specific project requirements. For further information about Viem, please visit [https://viem.sh/docs/introduction](https://viem.sh/docs/introduction).
+
+| Feature               | Viem                                                                 | Ethers.js                               |
+|-----------------------|----------------------------------------------------------------------|-----------------------------------------|
+| Performance           | [Optimized for speed](https://viem.sh/docs/introduction#performance) | Reliable performance                    |
+| API Design            | Intuitive, developer-friendly                                        | Well-designed, widely used              |
+| Documentation         | Comprehensive and clear                                              | Good, but may vary by feature           |
+| Debugging             | Advanced debugging tools                                             | Standard debugging capabilities         |
+| Ecosystem Integration | Seamless integration with certain tools                              | Broad integration with many tools       |
+
+Viem already includes out-of-the-box configuration for Hedera public networks: [testnet, mainnet, and previewnet](https://github.com/wevm/viem/blob/cc105f801ec69640d3d806d86b35e36002d8c912/src/chains/index.ts#L113-L115).
+
+## Project Files and Folders
+
+- `hardhat.config.js` - This is the configuration file for your Hardhat project development environment. It centralizes and defines various settings like Hedera networks, Solidity compiler versions, plugins, and tasks.
+
+- `/contracts` - This folder holds all the Solidity smart contract files that make up the core logic of your dApp. Contracts are written in `.sol` files.
+
+- `/test` - This folder contains test scripts that help validate your smart contracts' functionality. These tests are crucial for ensuring that your contracts behave as expected.
+
+-  `/scripts` - This folder contains essential JavaScript files for tasks such as deploying smart contracts to the Hedera network. 
+
+- `.env.example` - This file is contains the environment variables needed by the project. Copy this file to a `.env` file and fill in the actual values before starting the development server or deploying smart contracts. To expedite your test setup and deployment, some variables are pre-filled in this example file.
+
+## Setup
+
+1. Clone this repo to your local machine:
+
+```shell
+git clone https://github.com/hashgraph/hedera-json-rpc-relay.git
+```
+
+2. Once you've cloned the repository, open your IDE terminal and navigate to the root directory of the project:
+
+```shell
+cd hedera-json-rpc-relay/tools/hardhat-viem-example
+```
+
+3. Run the following command to install all the necessary dependencies:
+
+```shell
+npm install
+```
+
+4. Get your Hedera testnet account hex encoded private key from the [Hedera Developer Portal](https://portal.hedera.com/register) and update the `.env.example` `TESTNET_OPERATOR_PRIVATE_KEY`
+
+5. Copy `.env.example` to `.env`
+
+6. Run the test script from the root directory of the project. The default network is set to "local."
+
+```shell
+# runs test on default network
+npx hardhat test
+
+# runs test on testnet 
+npx hardhat test --network testnet
+```
+
+Expect an output similar to the following:
+```shell
+  RPC
+The address 0xe0b73F64b0de6032b193648c08899f20b5A6141D has 10000000000000000000000 weibars
+    ✔ should be able to get the account balance (1678ms)
+Greeter deployed to: 0xD9d0c5C0Ff85758BdF05A7636F8036d4D065F5B6
+    ✔ should be able to deploy a contract (11456ms)
+Contract call result: initial_msg
+    ✔ should be able to make a contract view call (1249ms)
+Updated call result: updated_msg
+Contract call result: updated_msg
+    ✔ should be able to make a contract call (6806ms)
+
+
+  4 passing (22s)
+```
+
+7. Run the following command to deploy the smart contract. 
+```shell
+# deploys to the default network
+npx hardhat deploy-contract
+
+# deploys to testnet
+npx hardhat deploy-contract --network testnet
+```
+
+# Contributing
+Contributions are welcome. Please see the
+[contributing guide](https://github.com/hashgraph/.github/blob/main/CONTRIBUTING.md)
+to see how you can get involved.
+
+# Code of Conduct
+This project is governed by the
+[Contributor Covenant Code of Conduct](https://github.com/hashgraph/.github/blob/main/CODE_OF_CONDUCT.md). By
+participating, you are expected to uphold this code of conduct. Please report unacceptable behavior
+to [oss@hedera.com](mailto:oss@hedera.com).
+
+# License
+[Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0)

tools/hardhat-viem-example/contracts/Greeter.sol

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+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.9;
+
+contract Greeter {
+    string private greeting;
+
+    event GreetingSet(string greeting);
+
+    //This constructor assigns the initial greeting and emit GreetingSet event
+    constructor(string memory _greeting) {
+        greeting = _greeting;
+
+        emit GreetingSet(_greeting);
+    }
+
+    //This function returns the current value stored in greeting variable
+    function greet() public view returns (string memory) {
+        return greeting;
+    }
+
+    //This function sets the new greeting msg from the one passed down as parameter and emit event
+    function setGreeting(string memory _greeting) public {
+        greeting = _greeting;
+
+        emit GreetingSet(_greeting);
+    }
+}

tools/hardhat-viem-example/hardhat.config.js

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+require("@nomicfoundation/hardhat-toolbox-viem");
+require("@nomicfoundation/hardhat-chai-matchers");
+const { task } = require("hardhat/config");
+
+// Import dotenv module to access variables stored in the .env file
+require("dotenv").config();
+
+// Define Hardhat tasks here, which can be accessed in our test file (test/rpc.js) by using hre.run('taskName')
+task("show-balance", async () => {
+  const showBalance = require("./scripts/showBalance");
+  return showBalance();
+});
+
+task("deploy-contract", async () => {
+  const deployContract = require("./scripts/deployContract");
+  return deployContract();
+});
+
+task("contract-view-call", async (taskArgs) => {
+  const contractViewCall = require("./scripts/contractViewCall");
+  return contractViewCall(taskArgs.contractAddress);
+});
+
+task("contract-call", async (taskArgs) => {
+  const contractCall = require("./scripts/contractCall");
+  return contractCall(taskArgs.contractAddress, taskArgs.msg);
+});
+
+/** @type import('hardhat/config').HardhatUserConfig */
+module.exports = {
+  mocha: {
+    timeout: 3600000
+  },
+  solidity: {
+    version: "0.8.9",
+    settings: {
+      optimizer: {
+        enabled: true,
+        runs: 500
+      }
+    }
+  },
+  // This specifies network configurations used when running Hardhat tasks
+  defaultNetwork: "local",
+  networks: {
+    local: {
+      // Your Hedera Local Node address pulled from the .env file
+      url: process.env.LOCAL_NODE_ENDPOINT,
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.LOCAL_NODE_OPERATOR_PRIVATE_KEY ? [process.env.LOCAL_NODE_OPERATOR_PRIVATE_KEY] : []
+    },
+    testnet: {
+      // HashIO testnet endpoint
+      url: 'https://testnet.hashio.io/api',
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.TESTNET_OPERATOR_PRIVATE_KEY ? [process.env.TESTNET_OPERATOR_PRIVATE_KEY] : []
+    },
+
+    /**
+     * Uncomment the following to add a mainnet network configuration
+     */
+    mainnet: {
+      // HashIO mainnet endpoint
+      url: 'https://mainnet.hashio.io/api',
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.MAINNET_OPERATOR_PRIVATE_KEY ? [process.env.MAINNET_OPERATOR_PRIVATE_KEY] : []
+    },
+
+    /**
+     * Uncomment the following to add a previewnet network configuration
+     */
+    previewnet: {
+      // HashIO previewnet endpoint
+      url:'https://previewnet.hashio.io/api',
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.PREVIEWNET_OPERATOR_PRIVATE_KEY ? [process.env.PREVIEWNET_OPERATOR_PRIVATE_KEY] : []
+    }
+  }
+};