Add a top-level doc for authenticating with RBTools.
Review Request #12343 — Created June 6, 2022 and submitted
RBTools authentication has never been explicitly documented (outside of
the small doc for
rbt login). With the coming inclusion of SSO support
in Review Board, we need a much more visible set of instructions for
logging in with RBTools, especially with API tokens. This change adds
that to the manual.
Built HTML and checked the output.