Add release notes for Review Board 5.0 RC 1.
Review Request #12611 — Created Sept. 19, 2022 and submitted — Latest diff uploaded
This is hopefully the last pre-release for 5.0. This features control of
token expiration, notification when expired tokens are being used, improved
Ship It status in the dashboard, and some bug fixes.
Built the docs. Checked for bad links, build errors, and spelling errors.