fix: Correct workflow to add the changed README.md file to the git commit that exists within the etc/PackageTemplate directory.

Author: paulhazen

.github/workflows/unity-version-badge.yml

@@ -30,5 +30,6 @@ jobs:
           git config --global user.name 'github-actions'
           git config --global user.email '[email protected]'
           git add README.md
+          git add etc/PackageTemplate/README.md
           git commit -m "Update Unity version badge to $UNITY_VERSION"
           git push