Configure dependabot to check github-actions updates (#3333)

* Configure dependabot to check github-actions updates

Some actions based on Node 16 are deprecated.

See https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20.

* Under /.github

https://docs.github.com/en/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot#example-dependabotyml-file-for-github-actions

* Try /.github/workflows

* Update .github/dependabot.yml

Co-authored-by: Zongle Wang <wangzongler@gmail.com>

---------

Co-authored-by: Tingluo Huang <tingluohuang@github.com>

.github/dependabot.yml

@@ -5,6 +5,11 @@ updates:
   schedule:
     interval: "daily" 
   target-branch: "main" 
+- package-ecosystem: "github-actions"
+  directory: "/"
+  schedule:
+    interval: "daily" 
+  target-branch: "main" 
 - package-ecosystem: "nuget"
   directory: "/src"
   schedule: