Update mergify.yml (#435)

(cherry picked from commit 36aa372)

# Conflicts:
#	.github/mergify.yml

.github/mergify.yml

@@ -0,0 +1,51 @@
+pull_request_rules:
+  - name: Backport to humble at reviewers discretion
+    conditions:
+      - base=master
+      - "label=backport-humble"
+    actions:
+      backport:
+        branches:
+          - humble
+
+  - name: Backport to iron at reviewers discretion
+    conditions:
+      - base=master
+      - "label=backport-iron"
+    actions:
+      backport:
+        branches:
+          - iron
+
+  - name: Ask to resolve conflict
+    conditions:
+      - conflict
+      - author!=mergify[bot]
+      - author!=dependabot[bot]
+    actions:
+        comment:
+          message: This pull request is in conflict. Could you fix it @{{author}}?
+
+  - name: Ask to resolve conflict for backports
+    conditions:
+      - conflict
+      - author=mergify[bot]
+    actions:
+        comment:
+          message: This pull request is in conflict. Could you fix it @bmagyar @destogl @christophfroehlich @saikishor?
+
+  - name: development targets master branch
+    conditions:
+      - base!=master
+      - author!=bmagyar
+      - author!=destogl
+      - author!=christophfroehlich
+      - author!=saikishor
+      - author!=mergify[bot]
+      - author!=dependabot[bot]
+    actions:
+        comment:
+          message: |
+            @{{author}}, all pull requests must be targeted towards the `master` development branch.
+            Once merged into `master`, it is possible to backport to `{{base}}`, but it must be in `master`
+            to have these changes reflected into new distributions.