Warn before closing all windows

[lee-tts]

First off, great extension! Much appreciated.

I found out the hard way that clicking the extension's button is a nuclear option to close all windows except the one in focus. Some warning would be nice! :D

If there was a way to have a popup with a 'don't show again' tickbox the first time you press the button ... or some other option (even a note in the extension description).