add dependabot for github actions updates

Author: purificant

.github/dependabot.yml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: monthly
+    open-pull-requests-limit: 5
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+    commit-message:
+      prefix: ci
+      include: scope