GitLab

As agreed during the 2020-01 community call [1] this patch introduces a
changelog, based on the principles explained at keepachangelog.com [2].
A new MAINTAINERS entry is also added, with myself as (currently sole)
maintainer.

[1] See C.2 at https://cryptpad.fr/pad/#/2/pad/edit/ERZtMYD5j6k0sv-NG6Htl-AJ/
[2] https://keepachangelog.com/en/1.0.0/

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Acked-by: Lars Kurth <lars.kurth@citrix.com>
Acked-by: Wei Liu <wl@xen.org>