workflow: update github actions via dependabot (#5656)

.github/dependabot.yml

@@ -62,3 +62,9 @@ updates:
   - dependency-name: node-notifier
     versions:
     - 8.0.1
+- package-ecosystem: "github-actions"
+  directory: "/"
+  schedule:
+    interval: monthly
+  open-pull-requests-limit: 10
+  versioning-strategy: lockfile-only