Add docs links to MR settings page

The following discussion from !50383 (merged) should be addressed:

• @aqualls started a discussion: (+1 comment)

  suggestion (non-blocking): I think links to explain what fast-forward merges -- and possibly rebases -- are would be a net benefit here. However, what's here works, and given the complexity this MR has seen already, I'd vote for handling it in a follow-up.