Describe the bug
The ZSH completion instructions should include guidance for those using "Oh My Zsh" plugin.

To Reproduce
N/A.

Expected behavior
In the section https://github.com/tofuutils/tenv?tab=readme-ov-file#install-shell-completion , we should have zsh+Oh My Zsh instructions.

This guy explains a bit how zsh completion works:
https://stackoverflow.com/a/66145365/3538173

It's more the idiomatic way to add a new zsh completion with Oh My Zsh, and the completion filename MUST be _tenv.

Screenshots
N/A.

Environment (please complete the following information):

• OS: Ubuntu 22
• tofuenv version v1.11.6

Additional context
N/A.