ci: add mergify rules for release-v3.2
ci: add mergify rules for release-v3.2

added mergify rules for backporting and
for auto merging the PR.

Signed-off-by: Madhu Rajanna <60fbf37a92c2a0908e31296d18dadbec5a4dae17@gmail.com>

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi