Add setting to disable kubie's prompt

[sbstp]

@EItanya can you check if this does indeed fix your double prompt issue?

[EItanya]

Yup, that worked for me! Man you're quick, was about to do that myself this morning.
Hopefully I'm not overstepping here, but I wonder if it would be clearer from a code perspective to not inject the prompt code into the .rc file at all, rather than disabling it with another env var.

For examle something like what I have done here: https://github.com/EItanya/kubie/blob/disable-prompt-non-env/src/shell/zsh.rs

My approach could definitely use cleaning up, but it seems to me that doing this with magic env variables may lead to more confusion down the line.

let me know what you think!

[sbstp]

I think you're right. I wanted to do something simple and quick but the zshrc file is quickly getting messy.