Support shell completion for nushell

[LoicRiegel]

Is your feature request related to a problem? Please describe.
Hi,
I'm a contributor of the nushell project, and I think it would be really nice if oclif was able to generate shells completions for nushell using this plugin.
You can have a look at what custom completions for nushell look like in the nu_script repo, where those cusotm completions were added by the community.

Describe the solution you'd like
Nushell is supported, just like zsh, bash...

Describe alternatives you've considered
None

Additional context
I sadly won't be able to implement this, however; I can myself available for any questions and support regarding nu.

[cristiand391]

If any oclif user is interested in this feature please give a thumbs up ⬆

I don't think we can prioritize this in the near-future, and don't want people to open PRs without knowing if we can accept them first (if there's no interest from users, I would be fine waiting for nushell to reach v1 to even look at this).

Workaround:
use https://github.com/cristiand391/oclif-carapace-spec-plugin and carapace-spec to get completion in nushell for any oclif CLI.

[LoicRiegel]

Sure, sounds good!