chore: Included githubactions in the dependabot config

This should help with keeping the GitHub actions updated on new releases. This will also help with keeping it secure.

Dependabot helps in keeping the supply chain secure https://docs.github.com/en/code-security/dependabot

GitHub actions up to date https://docs.github.com/en/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot

https://github.com/ossf/scorecard/blob/main/docs/checks.md#dependency-update-tool
Signed-off-by: naveen <172697+naveensrinivasan@users.noreply.github.com>

Closes https://github.com/dart-lang/sdk/pull/49168

GitOrigin-RevId: afc9a321581047a18b4992663062c8148563ca61
Change-Id: I371263d2ee93375a2b9756b344ed70c7cdf14a66
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/247160
Reviewed-by: Alexander Thomas <athom@google.com>
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..5ace460
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"