Add option to select different prompt types

[csfh]

Hi @dhh

In this PR I've added a prompts directory similar to fonts and themes. This will allow a user to change to different kinds of prompts.

I don't suggest Omakub should ship with a ton of prompts, but perhaps a couple of standard ones, the default you have, something that looks like Pure, or my own "Avatar"-style and perhaps even a Powerline.

Additionally, I've also made some changes to that Omakub uses $OMAKUB_PATH throughout the code, this allowed me to develop and enable a local version of Omakub next to the one installed in ~/.local/share/omakub.

Last thoughts, it might make sense to rename OMAKUB_PATH to OMAKUB_HOME - while this is non essential, it does seem like _HOME suffix is more consistent with more libraries in my experiences.

For your convenience I've included a screenshot.

Lastly, thanks for creating this. Omakub has renewed my interest in a Linux based setup.

[csfh]

In the unlikely event you decide to merge this 😉 - please let me know first since I didn't set up my gpg key yet. I'd like to amend the commits with signatures if they're getting merged.

I was also thinking that, if configuring prompts is interesting then we should have a discussion about which to add to this branch before it's merged.

[csfh]

Signed both commits.

[dhh]

@csfh Can you show what the different prompts look like with some screenshots? Thanks for working on this!

[csfh]

Yeah. Let me a maybe add two more for a total of four. I'm not a big prompt-aficionado, but I'll try to cover some of the important ground.

[csfh]

This is "Avatar" - a prompt inspired by Pure which is for zsh, https://github.com/sindresorhus/pure.

[mandarvaze]

@csfh Have you considered https://starship.rs/ for prompts ? It is far superior and cross platform and works will all the shells

[csfh]

Good idea. I will look at starship too!