[Contribution] ZSH Completion file

[obeone]

Hi,

I (no ok, not me, GPT-4) created a very performant ZSH completion file for sgpt command. You can find it here, fell free to add it to the project: https://gist.github.com/obeone/dc66f2ca40b8254edab61ac50cdec0f3

To give some context: While working on a custom GPT "ZSH Expert" that I am creating, I tested asking it for a completion for sgpt, and the result is surprisingly very good!

[obeone]

I made some change to the original script :

• The completion of the role was bugged; it indicated .json at the end of role and it was not compatible with the expected arguments. The extension is now correctly filtered; however, if you have been impacted by the problem, you have to manually delete the existing cache of roles : rm ~/.cache/sgpt_roles
• Removing caches on chats, it was impossible to detect their creation of a new chat and therefore invalidate this cache. It is still retained on roles, even if the same defect is present. Because roles, to me, do not change every hours.