Add support for zsh-fast-syntax-highlighting

[motheki]

Hello,

I would like to add support for zsh-fast-syntax-highlighting which has marginally better performance than zsh-syntax-highlighting, to the zsh configuration module in nix-darwin.

The repository can be found here

There is an existing nix package for zsh-fast-syntax-highlighting here

[Samasaur1]

Would there be any problems if both zsh-syntax-highlighting and zsh-fast-syntax-highlighting are enabled at the same time?

[motheki]

@Samasaur1 Not from my testing. I have had both enabled at multiple points in time and zsh-fast-syntax-highlighting seems to take precedence.

[Samasaur1]

I think there should still probably be a warning when both options are enabled, since zsh-syntax-highlighting won't take effect if both are enabled.

[motheki]

@Samasaur1 Thank you for your patience. I took some time to add a warning that Zsh-Syntax-highlighting and zsh-fast-synatx-highlighting are mutually exclusive. Let me know if there is anything else that needs to be addressed.