Configure Dependabot to check for outdated actions used in workflows

Dependabot will periodically check the versions of all actions used in the repository's workflows. If any are found to
be outdated, it will submit a pull request to update them.

NOTE: Dependabot's PRs will occasionally propose to pin to the patch version of the action (e.g., updating
`uses: foo/bar@v1` to `uses: foo/[email protected]`). When the action author has provided a major version ref, use that instead
(e.g., `uses: foo/bar@v2`). Dependabot will automatically close its PR once the workflow has been updated.

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

Author: per1234

Diff for: .github/dependabot.yml

@@ -0,0 +1,15 @@
+# See: https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#about-the-dependabotyml-file
+version: 2
+
+updates:
+  # Configure check for outdated GitHub Actions actions in workflows.
+  # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/dependabot/README.md
+  # See: https://docs.github.com/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot
+  - package-ecosystem: github-actions
+    directory: / # Check the repository's workflows under /.github/workflows/
+    assignees:
+      - per1234
+    schedule:
+      interval: daily
+    labels:
+      - "topic: infrastructure"