Add Gradient API

[thiccaxe]

closes #928

[thiccaxe]

• [x] gradient API
• [ ] update minimessage to use this API
  • [ ] gradients
  • [ ] stops?
  • [ ] rainbows
• [X] deprecate TextColor#lerp
• [X] add other gradients
  • [X] figure out how to deal with the new colorspace
  • [X] Linear RGB
  • [X] OkLab
  • [ ] OkLCH
• [ ] tests
  • [ ] RGB
  • [ ] HSV
  • [ ] LAB
  • [ ] OKLAB
  • [ ] LCH
  • [ ] OKLCH
  • [ ] minimessage

[thiccaxe]

decided to rework this in https://github.com/thiccaxe/adventure-gradient

Resolves the main concern in

Idk if it's just me, but it seems weird to have interpolation methods on the gradient? I don't really have an better API design but something about that feels off to me. Like, they are just util methods and can be used for other stuff, its a bit weird to tie them to the concept of a gradient?

Now interpolation is kept separate from the gradient business. No need for extra implementations per-gradient type.