github-action: add dependabot for GitHub actions (#155)

Author: v1v

.github/dependabot.yml

@@ -9,3 +9,16 @@ updates:
     directory: "/" # Location of package manifests
     schedule:
       interval: "daily"
+
+  - package-ecosystem: "github-actions"
+    directories:
+      - "/"
+      - "/.github/actions/*"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+      time: "22:00"
+    groups:
+      github-actions:
+        patterns:
+          - "*"