frontend: Example file automating tagging

Ensure this is part of our chart templating + preparing RC step.

https://github.com/GoogleCloudPlatform/prometheus-engine/commit/e2cd07628f5bf3be5dc794ce8f4d4b9a206447ec#diff-6310bb1ec887ba29736ce70fa2bbe0d51c1f93a24c3044033d4d6ce7eb76c595