Pull in example repositories

[gakonst]

Currently, we have 3 kinds of examples:

• waffle: https://github.com/ethereum-optimism/Truffle-ERC20-Example
• truffle: https://github.com/ethereum-optimism/Waffle-ERC20-Example
• hardhat: https://github.com/ethereum-optimism/optimism-tutorial

These should all be pulled in this repo under an examples/ directory, and tested in CI. IMO showing the step-by-step evolution of the example repo is better done as content in a blogpost/for the community hub, and not for the github repo

[smartcontracts]

This is done now