Pull request workflow

1. Use GitHub keywords to close the issue (e.g. fixes #1, closes #1, resolves #1) in the body of the PR content
2. Move to the “Review” pipeline when it’s ready for review (ZenHub)
3. Add reviewer when it’s ready for review
4. Connect the PR to the issue with the ZenHub feature
5. After the PR is merged, someone adds a note to the release notes draft (either the merger or PR opener).