Add toggle keybinding

[jabcross]

When learning a new set of shortcuts, it is sometimes useful to be able to easily revert to the default keybindings easily (if you're in a hurry or need to focus, such as during a presentation). I've often had to disable the whole extension altogether to achieve this, but a builtin command would be very useful.

Is this an existing functionality? Maybe it could be implemented with a "disabled" mode without any keybindings.

[bezbac]

I believe that this was previously discussed in #189, and as you suggested, this can be done using a disabled mode. See: https://github.com/71/dance/issues/189#issuecomment-898893176

[jabcross]

Thanks. I do think this should be the default and that there should be a command and default keybinding for this, though.