feat: implement hex formatting support

[rubyowo]

Closes catppuccin/whiskers#8

I'd like to refactor this in the future or sometime else, it's a bit ugly currently.

[backwardspy]

just dropping an update on this; i've not forgotten about it but i haven't had the time so far to give it the review it deserves. i should be able to work on it in the coming days.

[sgoudham]

Caught up with @backwardspy on discord, he still plans on coming back to this and would like to have an input in it 👍

[nullishamy]

Speaking broadly, I'm not super into having loads of extra parameters everywhere. Can we somehow centralise this? Also not a fan of the String type being used here, I think at least a type alias to describe what the format represents would be a good improvement at, perhaps a struct that can handle the rendering too, let's see.