Removing .html extension from URLs in Google Cloud Storage

I have a collection of static pages stored in a Google Cloud Storage bucket. NOTE: Not App Engine.

In years gone by I would have used a .htaccess file to remove the URL extensions, but with some research I've seen that Google uses app.yaml files for this.

My static html pages, as well as the app.yaml file are in the root folder of the bucket.

The app.yamil file contains:

- url: /(.+)
  mime_type: text/html
  static_files: static/\1.html
  upload: static/(.+)

What am I missing?

Thanks, Chris