Add contribution guidelines

README.md

@@ -100,6 +100,11 @@ inconsistencies (that aren't a result of legacy APIs) file an issue.
   no support of transpilation to ES5, no support of polyfills, etc
 - Support special functionality of obsolete HTML elements (`<marquee>`, etc)
 
+## Contribution Guidelines
+- Ensure your changes pass the tests below.
+- To ensure the code follows Deno's formatting guidelines, use the built-in deno fmt command. This will automatically format your TypeScript files to match Deno's code style. Run: ``sh deno fmt``
+- When implementing new features for Deno DOM, ensure that the standard algorithm outlined by the [DOM Living Standard][https://dom.spec.whatwg.org/] is followed. Any deviations from the spec should be documented clearly in the code and pull request descriptions.
+
 ## Running tests
 
 To run tests (excluding WPT tests) use the following for WASM