Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55383
Adds a branch targeting validation that replaces the equivalent Danger.js check.
The check validates that PRs target either `main` or a `-stable` branch, and
automatically adds the "Pick Request" label when targeting stable branches.
- Created `checkBranchTarget.js` - pure function returning validation message
- Added check step to `annotate-pr.yml` that calls the JS and adds labels
- Added `issues: write` permission for label functionality
Changelog: [Internal]
Reviewed By: huntie
Differential Revision: D91685081
fbshipit-source-id: 87e7124f7d825b51cb791dc94720c487ff95d414
