feat: enable task autocompletion

[cristianoliveira]

Hey there! There is a missing feature for nrr which is something similar to npm completion so one can add scripts autompletion into zsh (or any other shell). Since the project uses clap, it should be quite straightforward to achieve that with clap_complete. I was thinking to create a PR but I'm not sure this is something that is align with the project direction

Thanks in advance. Let me know I can create a PR :)

[cristianoliveira]

I have recently done that on a small tool I'm working on: https://github.com/cristianoliveira/pono