Improve guide on working with the Paper source code

[Strokkur424]

I think it could be nice to include more information on how to work with Paper's source code. This would include not only information for contributors, kinda how we already have the Events page, but also information regarding how to correctly fork Paper (use paperweight to do so) and maintain your own fork could be part of that category.

The following pages are what came to mind first. I wish to ask for anybody to suggest more pages or changes to these:

Page name	Page content
Contributing to Paper	How to open a PR, what to watch out for, basically CONTRIBUTING.md in the main repo
Styling guidelines	Perhaps a dedicated page to certain guidelines, like imports, // Paper comments, and similar
Forking Paper	A page explaining how to create and maintain your own fork of Paper using paperweight

Opening this as an issue first, since I want to have some input whether anybody thinks this is really needed in the first place. We already have this one Events contribution page without much context around it, so I think it could be good to extend onto that.

[MiniDigger]

Contributing to Paper should mention that bigger changes should be discussed in an issue first.
not sure if a forking paper page is needed. its an advanced topic and we don't really provide support for that, other than throwing the tooling and example repo at people.

[Strokkur424]

That's a very good point. It should avoid that people do 2k line PRs and end up being rejected because it doesn't fit the scope of an API.

Furthermore, the forking page could just be a very quick reference to where you can find information about it, doesn't have to be a full-on guide. Just so that we have something to throw at people who ask in #paper-dev on how to create a fork. With all the tooling in the right place. I think people who really need to fork, will somehow figure it out

[Leguan16]

It should avoid that people do 2k line PRs

It won't avoid it as not all contributors will read that guide. We can only do as much to minimize the amount of huge PRs that get rejected in the end.

A how to create a Paper fork page sounds nice in general.