docs(codestyle): add empty code style document

.github/CODE_STYLE.md

@@ -0,0 +1 @@
+# Code style

.github/CONTRIBUTING.md

@@ -14,6 +14,8 @@ The [Polkadot Runtime Specification](https://research.web3.foundation/en/latest/
 
 One important distinction is that we are building the Polkadot Runtime Environment, not Polkadot itself. Given that, although a deep understanding of Polkadot is helpful, it's not critical to contribute to gossamer. To help understand how the Runtime Environment relates to Polkadot, check out this [talk that one of our team members gave at DotCon](https://www.youtube.com/watch?v=nYkbYhM5Yfk).
 
+For coding style, you may refer to the [code style](CODE_STYLE.md) document which we keep up to date with coding style conventions we have for this repository.
+
 ## Contribution Steps
 
 1. **Fork the gossamer repo.**

README.md

@@ -128,7 +128,7 @@ To start the polkadot node:
 
 ## Contribute
 
-- Check out [Contributing Guidelines](.github/CONTRIBUTING.md)  
+- Check out [Contributing Guidelines](.github/CONTRIBUTING.md) and our [code style](.github/CODE_STYLE.md) document
 - Have questions? Say hi on [Discord](https://discord.gg/Xdc5xjE)!
 
 ## Donate