ci: add mergify rules for release 3.3

as we have a new release-v3.3 branch. adding
the mergify rules for auto merge and auto backport
based on backport-to-release-v3.3 label.

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

.mergify.yml

@@ -228,6 +228,41 @@ pull_request_rules:
       merge: {}
       dismiss_reviews: {}
       delete_head_branch: {}
+  - name: backport patches to release-v3.3 branch
+    conditions:
+      - base=devel
+      - label=backport-to-release-v3.3
+    actions:
+      backport:
+        branches:
+          - release-v3.3
+  # automerge backports if CI successfully ran
+  - name: automerge backport release-v3.3
+    conditions:
+      - author=ceph-csi-bot
+      - base=release-v3.3
+      - label!=DNM
+      - "#approved-reviews-by>=1"
+      - "status-success=codespell"
+      - "status-success=multi-arch-build"
+      - "status-success=go-test"
+      - "status-success=golangci-lint"
+      - "status-success=gosec"
+      - "status-success=commitlint"
+      - "status-success=mod-check"
+      - "status-success=lint-extras"
+      - "#changes-requested-reviews-by=0"
+      - "status-success=ci/centos/mini-e2e-helm/k8s-1.19"
+      - "status-success=ci/centos/mini-e2e-helm/k8s-1.20"
+      - "status-success=ci/centos/mini-e2e/k8s-1.19"
+      - "status-success=ci/centos/mini-e2e/k8s-1.20"
+      - "status-success=ci/centos/upgrade-tests-cephfs"
+      - "status-success=ci/centos/upgrade-tests-rbd"
+      - "status-success=DCO"
+    actions:
+      merge: {}
+      dismiss_reviews: {}
+      delete_head_branch: {}
   - name: remove outdated approvals on ci/centos
     conditions:
       - base=ci/centos