ci(Mergify): configuration update (#847)

Signed-off-by: Daniel Farina <null>

.mergify.yml

+queue_rules:
+  - name: default
+    conditions:
+      - "#approved-reviews-by>1"
+
+pull_request_rules:
+  - name: automerge to the base branch with label automerge and branch protection passing
+    conditions:
+      - "#approved-reviews-by>1"
+      - base=main
+      - label=automerge
+    actions:
+      queue:
+        name: default
+        method: squash
+        commit_message_template: |
+           {{ title }} (#{{ number }})
+           {{ body }}
+  - name: backport patches to v3.x branch
+    conditions:
+      - base=main
+      - label=backport/v3.x
+    actions:
+      backport:
+        branches:
+          - v3.x
+  - name: backport patches to v4.x branch
+    conditions:
+      - base=main
+      - label=backport/v4.x
+    actions:
+      backport:
+        branches:
+          - v4.x
+  - name: backport patches to v5.x branch
+    conditions:
+      - base=main
+      - label=backport/v5.x
+    actions:
+      backport:
+        branches:
+          - v5.x
+  - name: backport patches to v6.x branch
+    conditions:
+      - base=main
+      - label=backport/v6.x
+    actions:
+      backport:
+        branches:
+          - v6.x