Add development documentation

[jacobsandersen]

This PR is a pretty big undertaking and help is welcomed, but I plan to keep cracking at it either way until it's good enough to go in.

So far, this is just some scaffolding with very little real content to go in. Input welcome for ideas of what to add.

This PR's goal is to eventually provide (at least a starting point for) a comprehensive user guide for development on Paper platforms (Paper/Waterfall). JavaDocs exist, and there are some guides floating around in sparse corners of the Internet, but a centralized location is probably better.

Draft for now, and potentially for a good amount of time still.

p.s. idk what to do about the merge commit :^) if someone wanna edumucate me feel free

[aurorasmiles]

It was suggested that we could maybe add some sort of styling "guidelines" for plugin configs, maybe that might be something to also add into this PR

[mrfloris]

It was suggested that we could maybe add some sort of styling "guidelines" for plugin configs, maybe that might be something to also add into this PR

This is what I use internally and have collected / expanded on over the years, and I hope it's of some use to others. Maybe this could be used to get started, I am sure I am perhaps incorrect here and there, or am missing some important points.

yaml-styleguide-mrfloris.md

[jacobsandersen]

plan to work on this in the next few weeks when school is over for the winter

[e-im]

Thanks so much for your initial work on this. Developer docs will be continued as part of our new documentation (PaperMC/docs#19)