Describe the new feature or change to an existing feature you'd like to see

Enable Renovate updating for dependencies scoped under the @ampproject namespace – these are intended to update AMP when released.

Describe alternatives you've considered

Alternatives:

1. Build a seperate automatic upgrade system to enable this feature set.
2. Manually update each @ampproject dependency on each release.

Additional context

We're trying to tighten up the release cycle between WorkerDOM updates and their availability in amp-script.