ci(deps): extend dependabot coverage to every manifest

新增 1 条 update 配置：github-actions@/
这些清单此前没有任何 dependabot 条目，CVE 扫描完全覆盖不到。

Author: FasterEdge

.github/dependabot.yml

@@ -0,0 +1,11 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+      day: monday
+    open-pull-requests-limit: 5
+    labels:
+      - dependencies
+      - security