Encapsulate all features

[Cahllagerfeld]

When adding new features to webstone, we should aim for encapsulating them as good as possible.

This would end up with a "base"-cli package, that contains basic fundamentals, like adding new pages and endpoints to a sveltekit application.

All additional functionality, like rest, authentication, should live inside their own packages with a convention webstone-<package-name>, e.g webstone-authentication.

As we're using Gluegun to power the CLI, we are able to create plugins that get picked up by the CLI, but ideally, we also use this package to also import functions, and other code from them.

[mikenikles]

I'd say we found an excellent way to deal with that :). #285 is living proof as the first plugin.