[Feature] Option for ESC to always close (ALT+F4)

[rotbus19]

As per title, an option to allow ESC to close immediately as though pressing `ALT+F4`.

Currently, it can take 3 x ESC to close the app (fullscreen -> Viewer -> Browser).

(This was discussed a looong time ago - https://forum.xnview.com/viewtopic.php? ... 9de3868d33)

[user0]

I think it should be implemented by:
1. adding Quit command to Settings>Shortcuts
2. allowing to reassign its shortcut from Ctrl+Q to Esc