feat: Create 'module' subcommand for creating, building, and managing modules repos

[gmpinder]

If we want a large ecosystem of modules created by other developers, we'll need a way to help them get started with creating these repos.

This new subcommand would have it's own build and new/init commands. The build command can manage all the CI and support building images for both GitHub and GitLab. The new and init commands will just create a new repo for a user to start with.

I don't see this as being too hard of a change to make considering most of the CI logic we have for user images is already done and we have signing capabillities.