Add initial description of recipes in README.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>
Reviewed-by: Frédéric Dalleau <frederic.dalleau@collabora.co.uk>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D7205

Based on version provided by Emanuele Aina.
Allows to create ospacks for all supported architectures and platforms.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D7203

Copying overlay and scripts from original repository
with adaptation for Debos.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>
Differential Revision: https://phabricator.apertis.org/D7201

Add configuration for arcanist, license file and short readme.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>

Differential Revision: https://phabricator.apertis.org/D7200