Add governance document

The idea of a better-defined governance model for wayland-protocols has
been discussed for quite a while [1].

A new GOVERNANCE document describes how changes to the wayland-protocols
repository are accepted. A set of members representing projects can vote
on merge requests sent via GitLab. The initial list of members is
available in the MEMBERS file.

[1]: https://lists.freedesktop.org/archives/wayland-devel/2019-February/040076.html



Signed-off-by: Drew DeVault <sir@cmpwn.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Acked-by: Daniel Stone <daniels@collabora.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Acked-by: Johan Helsing <johan.helsing@qt.io>
Acked-by: Roman Gilg <subdiff@gmail.com>
Acked-by: Christopher James Halse Rogers <raof@ubuntu.com>
Acked-by: Alan Griffiths <alan.griffiths@canonical.com>
Acked-by: Jonas Ådahl <jadahl@gmail.com>
Cc: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Cc: Carlos Garnacho <carlosg@gnome.org>
Cc: David Edmundson <david@davidedmundson.co.uk>