Add dependabot file for auto scan and update.

Signed-off-by: Jiewen Yao <[email protected]>

Author: jyao1

.github/dependabot.yml

@@ -0,0 +1,9 @@
+version: 2
+updates:
+
+  # Ref: 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
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      # Check for updates to GitHub Actions every week
+      interval: "weekly"