[Reviewers] Accept process docs

[Augie Fackler]

https://www.mercurial-scm.org/wiki/AcceptProcess <https://www.mercurial-scm.org/wiki/AcceptProcess> is now up to date as far as I'm aware, and should work for y'all. Non-accepters should be able to view the accept stamps, but not grant them.

I have some...elaborate configuration around all of this: https://bitbucket.org/snippets/durin42/74g9ME

In particular, the interactively-review alias is potentially of interest for accepters.