Chart: Optionally deploy an instance of docker-registry alongside docker_auth

[jthurner]

When the Chart was updated to Helm 3 there was some discussion around integrating docker-registry. The idea was dropped because helm-stable was shut down at the time and docker-registry had not found a new home.
Still, documentation and Chart reference the (not functional) integration, which is confusing:

• the "working example" has registry.enabled=true
• no clear description on how to configure the registry to link certificate/auth configuration

In the meantime, the docker-registry chart has been picked up by twuni. While not officially maintained by docker, it is a continuation of the chart in helm-stable and actively maintained.

Would you take a PR adding optional integration with docker-registry sourced from the chart by @twuni? I believe it makes a lot of sense to be able to manage both docker_auth and the registry in a single chart, and having the integration in the chart would also make it easier to understand how to deploy docker_auth alongside an existing registry.

[techknowlogick]

Oh indeed, a PR would be very much accepted:)