docs: tweak contributing guide

CONTRIBUTING.md

@@ -1,14 +1,17 @@
+# **footnotes** Contributing Guide
+
 **footnotes** welcomes contributions!
 
-Please follow these guidelines when contributing, as it will give your pull 
-request the best chance of being accepted:
+## Code of Conduct
 
-# Requesting Features/Reporting Bugs
+Please read and adhere to the project [Code of Conduct][coc].
+
+## Requesting Features/Reporting Bugs
 
 - To request a new feature or to report a bug, create an [Issue][new-issue] and 
   choose the correct template
 
-# Contributing Code
+## Contributing Code
 
 - **footnotes** uses [GitHub Flow][github-flow]
 - branch off of `main` to start developing (`git checkout -b <your branch>`)
@@ -21,20 +24,21 @@ request the best chance of being accepted:
   assigned to a Project board, this will automatically move it and any related
   Issues into the ‘Review in progress’ bucket
 
-# Commits
+## Commits
 
 - **footnotes** uses [Conventional Commits][conventional-commits]
 - we use [PHP Commitizen][php-commitizen] to automate this - use `composer commit`
 - keep individual commits as small as possible
 
-# Versioning
+## Versioning
 
 - **footnotes** uses [Semantic Versioning][semver]
 
-# Translating
+## Translating
 
 - Translations are welcome!
 
+[coc]: https://github.com/markcheret/footnotes/blob/main/CODE_OF_CONDUCT.md
 [new-issue]: https://github.com/markcheret/footnotes/issues/new/choose
 [github-flow]: https://githubflow.github.io/
 [pull-request]: https://github.com/markcheret/footnotes/compare