Update dependabot.yml to ensure proper labeling for GitHub Actions updates (#3)

## Description

This pull request makes a small configuration improvement to Dependabot
by automatically applying relevant labels to pull requests for GitHub
Actions updates.

* Added `dependencies` and `github-actions` labels to Dependabot PRs for
GitHub Actions updates in `.github/dependabot.yml`.

Author: MariusStorhaug

.github/dependabot.yml

@@ -7,5 +7,8 @@ version: 2
 updates:
   - package-ecosystem: github-actions # See documentation for possible values
     directory: / # Location of package manifests
+    labels:
+      - dependencies
+      - github-actions
     schedule:
       interval: weekly