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

.github/dependabot.yml

@@ -10,3 +10,13 @@ updates:
   labels:
   - dependencies
   versioning-strategy: widen
+ - package-ecosystem: "github-actions"
+  directory: "/"
+  schedule:
+    interval: daily
+    time: "04:00"
+    timezone: Europe/Berlin
+  open-pull-requests-limit: 20
+  labels:
+  - dependencies
+  versioning-strategy: widen