[Feature] Add keymap support for open/closed brackets -- i.e. [],<>,(),{}

[sjsimpson]

I have been trying to add ] as my shortcut for toggle-focus but haven't been able to, and I don't really want to have <C-letter> as my shortcut. Would be nice if there was a way to use these.

There may currently be, but I haven't been able to do it, and judging from key.ps they aren't currently mapped. I've never written anything in rust though, so I could be totally wrong.

Thank you! This is a very cool tool and I'm stoked to be using it.