Rated 5 out of 5 stars

le Firefox user 2ae55a ar Noll. 18, 2016 · buan-nasc

Works on Firefox Developer Edition 52.0a2 and Gnome 3.22.2...
Also there is a setting to hide the title bar even when the window is not maximized.Double-clicking does not minimize/maximize though.....for those of you who were wondering.:-P
Thanks for this awesome Add-on!