Create CONTRIBUTING.md to help people interested in contributing to Redox

Created by: polymetric1

Alot of the information provided in this file is copied from #336. It's still quite unfinished, in fact some sections are completely blank, but it's something to go on. If you don't have time to add to it yourself, feel free to just reply with a quick summary here and I (or someone else) will see what can be done. I myself am not the best explainer in the world however, it's probably best someone checks this. Sometimes I change my mind about what I'm writing in the middle of a sentence, and it comes out as gibberish. I don't think that happened much in here, I fixed most of that. Also, the information itself may not be completely accurate as I am not very familiar with this repository. In fact, it might be a good idea to put it into a separate branch in the main repo while it is worked on as I'm not sure it's ready to be displayed on the front page. I didn't change README.md, so it still isn't referenced from there. Honestly I think someone should look over this before it's displayed up front.