add documentation for the various about:config variables specific to Zen #187
Description
I've seen a lot of videos online (specifically https://www.youtube.com/watch?v=9G5PtUwdFkY and https://www.youtube.com/watch?v=SCMmzbxUqpo) that falsely assume Zen doesn't have the options to force window controls to the left, or create a new tab with Ctrl+T, when in reality these are just flags in the about:config. I think it would be good to at least create documentation that details the flags specific to Zen, especially since most of the existing info is only on the discord. (worst case scenario, i can write it and make a PR)