Update dependabot and mergify

Author: christophfroehlich

.github/dependabot.yml

@@ -11,3 +11,10 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+  - package-ecosystem: "github-actions"
+    # Workflow files stored in the
+    # default location of `.github/workflows`
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    target-branch: "humble"

.github/mergify.yml

@@ -0,0 +1,41 @@
+pull_request_rules:
+  - name: Backport to humble at reviewers discretion
+    conditions:
+      - base=master
+      - "label=backport-humble"
+    actions:
+      backport:
+        branches:
+          - humble
+
+  - 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 please fix it @christophfroehlich?
+
+  - name: development targets master branch
+    conditions:
+      - base!=master
+      - author!=bmagyar
+      - author!=christophfroehlich
+      - author!=nbbrooks
+      - 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.