Proposal: Pull code of conduct and contributing guides from individual repos and centralize here

[carsonfarmer]

I now have a pretty standard contributing guide I've been using everywhere which is quite comprehensive, and we already use the same code of conduct in all our repos. Maybe we can consolidate here, and then just add links to the readme in individual repos?

[carsonfarmer]

Here's an example of a pretty useful, but totally generic contributing guide: https://github.com/textileio/js-threads/blob/master/CONTRIBUTING.md and here's our CoC: https://github.com/textileio/js-threads/blob/master/CODE-OF-CONDUCT.md.