Translation Maintenance Guide

[tesseralis]

Hi everyone!

We're probably going to start new languages on Monday, so I've drafted a HOW-TO guide for starting your own language: https://gist.github.com/tesseralis/5ebff886823a0f7d9c905b617e755d59

This will probably go in a new repo (reactjs.org/reactjs-translations) along with the code for the bot.

Let me know if you have any suggestions for it!