Added release notes for Review Board 4.0 RC 1.
Review Request #11441 — Created Feb. 10, 2021 and submitted
This is a smaller release focused on tidying up installation and fixing
a few noted regressions. It is hopefully the final release before 4.0 is
Built the docs. Checked for spelling errors, build errors, and bad links.
Updated with the latest changes and info on Docker.
Revision 2 (+406 -4)