docs(README): add overrides section

[yannbf]

Issue: N/A

What Changed

Added a section about overriding rules in the README

Checklist

Check the ones applicable to your change:

• [ ] Ran yarn update-all
• [ ] Tests are updated
• [x] Documentation is updated

Change Type

Indicate the type of change your pull request is:

• [ ] maintenance
• [x] documentation
• [ ] patch
• [ ] minor
• [ ] major

[github-actions[bot]]

:rocket: PR was released in v0.4.0 :rocket: