hide the titlebar oleh nanpuyue

You need to install the script, otherwise this extension will not work:
https://gist.github.com/nanpuyue/ec7d34e174267db3927124edcd2a8844

Refer:
https://addons.mozilla.org/firefox/addon/minimize-the-window/
https://addons.mozilla.org/firefox/addon/maximize-the-window/
https://addons.mozilla.org/firefox/addon/close-the-window/