[docs] zsh completion instructions

[lonix1]

I want to enable zsh completions. (I'm using oh-my-zsh on ubuntu.)

The docs explain how to do so for bash, not zsh.

My completions for restic itself work, so I tried to do something similar to that:

resticprofile generate --zsh-completion | sudo tee /usr/local/share/zsh/etc/site-functions/resticprofile
sudo chmod +x /usr/local/share/zsh/site-functions/resticprofile

But that doesn't work.

How does one do this?