Create integration tests and trigger them on remote push events with GitHub Actions.

[HeavyMedl]

We experience a lot of fallout from changes to the NPM initializer. Occasionally when consumers scaffold a template with the initializer, their project template will break from some minor change. For example, we recently bumped @rei/cedar to 15. This major change renamed an asset we referenced in one of the templates, resulting in a build time error.

At a minimum, we should write an integration test that scaffolds and builds each template type. This will ensure changes to the initializer don't break downstream.

Once written, we should trigger these integration tests on remote push events with GitHub Actions.