gh-34999: Enable dependabot for github action updates
    
Enables automatic PRs from dependabot that update the versions of github
actions that we use in our workflow. Thus, we no longer need to do this
manually.

More details: https://docs.github.com/en/code-
security/dependabot/dependabot-version-updates/about-dependabot-version-
updates
    
URL: #34999
Reported by: Tobias Diez
Reviewer(s): Matthias Köppe

Author: Release Manager

.github/dependabot.yml

@@ -0,0 +1,10 @@
+# Documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  # Maintain dependencies for GitHub Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"