Fork repo and set up Continuous Deployment instead of one-shot deployment

The experience of the button is amazing: click, get something running.

But that's how you should deploy software. That's great for demos or for one-shot images that don't have to be updated, but not great for iterating on a codebase. Consequently, this limits the use cases for the button (we should not use the button for "boilerplate"-type repositories)

A more sustainable way for customers to go from GitHub to Cloud Run would be:

1. Fork the repo.
2. set up a Cloud Build Trigger to automatically deploy from the fork to Cloud Run
3. Run this trigger.

Maybe the button could help do that?

This would address along the way:

* https://github.com/GoogleCloudPlatform/cloud-run-button/issues/155
* https://github.com/GoogleCloudPlatform/cloud-run-button/issues/103