Add note about breaking releases

Author: mhauru

developers/contributing/index.qmd

@@ -113,6 +113,8 @@ Release notes:
 [YOUR RELEASE NOTES HERE]
 ```
 
+If you are making a breaking release, your release notes must also contain the string `Breaking changes` somewhere in them (this is mandated by the `@JuliaRegistrator` bot, described below).
+
 The `@JuliaRegistrator` bot will handle creating a pull request into the Julia central package repository and tagging a new release in the repository.
 The release notes should be a copy-paste of the notes written in `HISTORY.md` if such an entry exists, or otherwise (for a patch release) a short summary of changes.