`nuxi module add` check if module already installed

[pi0]

Discussed in #224

^{Originally posted by angelhdzmultimedia September 25, 2023}
Hi! Great job with nuxi! Big fan! 🔥🤯💚

It would be nice if nuxi module add checked if the package is already installed and avoid the installation step, and just continue with the pushing into the nuxt.config.ts modules: [] array.

Cheers

I think we could show a prompt to allow upgrade but also make sure not reinstalling when already seutp.

[adhamfarrag]

@pi0 can we introduce isInstalled utility via nypm ? Happy to work on it.