Bugzilla

We have a (very sparse) section on how to add docs to the `firefox-source-docs` here:
https://firefox-source-docs.mozilla.org/tools/moztreedocs/

But this is A) difficult to find as you need to scroll down past dozens of links to see it, and B) leaves out many important details and features of the system. We should move this to its own page that is linked to from the index and expand it to cover all the details necessary to use this system.