No documentation for android #268

Hi! I wasn't sure about where I would put this, and I can close this issue if need be but I noticed: https://www.reddit.com/r/firefox/comments/igv6bd/ff_android_missing_settings_for_local_sync_server/ is the only information I got on how to enable custom sync settings in firefox for android.

I'm not sure about where you would put something like that, but it would probably help someone else out in the future. Maybe a small section in the Readme would be nice!