* doc/contributing.texi (Contributing) [Reviewing the Work of Others]: New
section.
(Debbugs Usertags): Expound with Emacs Debbugs information and document the
'reviewed-looks-good' usertag.
* etc/git/gitconfig [b4]: New section.
Change-Id: I56630b15ec4fbc5c67e5420dbf2838556a005d6b
Reviewed-by: Ludovic Courtès <ludo@gnu.org>