Alful от McSinyx

This tiny script gives FireFox Quantum the ability to open new windows in Fullscreen mode. On startup it add a listener to set state to fullscreen every time a new window is open. The extension is supposed to be used with full-screen-api.ignore-widgets set to true to to hide the toolbars in windowed mode.

All credits go to tazeat, who wrote the original version and suggested the change to achieve the current behavior.