feat(bind): Support root binding

[znd4]

Hi, this is similar to a PR I just opened on sessionx, so down to close both if you don't like this implementation.

I haven't actually intentionally taken advantage of bash argument expansions before, so IDK what weird drawbacks there might be, but it's at least working on my machine 😅

[Mugworth]

You can also just run script directly: bind-key -n C-\ run-shell "~/.tmux/plugins/tmux-floax/scripts/floax.sh"