ci: add mr-label-maker configuration file
What does this MR do and why?
As of freedesktop/mr-label-maker!25 (merged) it can now load a project
configuration file from the target repository. This will be
hardcoded in the fdo-bots to read from .gitlab-ci/mr-label-maker.yml
,
see freedesktop/fdo-bots!19 (merged).
This configuration file is equivalent to mr_label_maker/mesa.py.