support for adding modules with subpath export

[danielroe]

e.g. https://louismazel.github.io/maz-ui-3/guide/nuxt

(related: https://github.com/nuxt/modules/pull/773/files)

[pi0]

We might auto detect subpath and also allow nuxi module add mazui/nuxt (which is not short) but wondering maybe would be good idea to support a field in modules DB as well?

[danielroe]

Exactly, I think it would be good to have something there that's the module to add to the modules array, if it's a subpath.