chore: get started with picker docs

[fdschmidt93]

I hope to have it finished by 0.1 :laughing: we should have this, then finally users can find some important stuff.

Lots to do

• [ ] Intro segment with examples
• [x] ~~Annotate picker methods~~ pretty much everything annotated already :partying_face:
• [ ] Complete Picker.new

Surely more things I cannot think of yet.

If anyone wants to help, please just make PRs / push straight away to the branch :)

[Conni2461]

Note that fps is still on going and is changing pickers.lua significant