docs(contrib): Add details for PRs with failing CI

files/en-us/mdn/community/pull_requests/index.md

@@ -132,6 +132,12 @@ When you are reviewing a pull request, you should:
   Tag the `@core-yari-content` team and ask if someone else can step in.
 - **Don't merge unless 'depends on'** pull requests are merged first.
 
+Don't merge pull requests that have failing tests.
+It is good [open source etiquette](/en-US/docs/MDN/Community/Open_source_etiquette) to keep the `main` branch stable to avoid disruption for contributors, maintainers, and for automated processes.
+An unstable `main` branch blocks all other pull requests and makes it difficult for others to review and merge contributions.
+In addition, contributors who watch repositories receive high volumes of notifications and unnecessary noise caused by failing tests can be frustrating.
+If you are not sure how to fix the failing tests, [ask for help](/en-US/docs/MDN/Community/Communication_channels) or assign the pull request to someone else.
+
 If a pull request looks good apart from small typos or other minor issues, you may want to fix the problem directly.
 You can do this provided the pull request [has been set up to allow changes](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork).
 It's recommended to use [comments with suggestions](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/commenting-on-a-pull-request#adding-line-comments-to-a-pull-request) for fixing minor issues, as they can be batched and committed in one go.