docs(README): add contribution guidelines

CONTRIBUTING.md

@@ -0,0 +1,25 @@
+# Contributing
+
+## How to contribute code
+
+### Commit messages
+
+This project uses [semantic-release](https://github.com/semantic-release/semantic-release) to automatically release when changes are merged to `main`.
+
+In order for this to work, commit messages must use [Angular Commit Message Conventions](https://github.com/angular/angular/blob/main/CONTRIBUTING.md#-commit-message-format), which in the simplest form looks like `<type>: <short summary>`. Below are some examples:
+
+- `feat: added new component`
+- `fix: fixed a bug`
+- `docs: updated documentation`
+
+If your change is a breaking change, this must be stated in the message, for example:
+
+```
+feat: updated some component
+
+BREAKING CHANGE: removes the '.subcomponent' class.
+```
+
+### What is a breaking change?
+
+A breaking change is any "incompatible API change". In the context of this design system, the API consists of CSS classes and SASS variables/functions/mixins etc. Any change which removes or renames a part of the API must be labelled a breaking change.

README.md

@@ -22,12 +22,6 @@ Start storybook:
 npm start
 ```
 
-## Project Structure
-
-Sass code roughly follows [The 7-1 Pattern](https://sass-guidelin.es/#the-7-1-pattern).
-
-Storybook stories should be placed alongside their respective component.
-
 ## Production build
 
 Build CSS: