add mergify
add mergify

Mergify automatically merges pull requests when they're ready so you
don't have to. You set the rules, it does the rest.

Signed-off-by: Sébastien Han <62d754cc350e84d3b1c32ae79f976f5348e74a40@redhat.com>

fgal/ceph-ansible,ceph/ceph-ansible,font/ceph-ansible,fgal/ceph-ansible,ceph/ceph-ansible,font/ceph-ansible