Feature request: help pop-up

[rbutoi]

Coming here from https://github.com/ynqa/jnv (which, thanks btw!), I wanted a quick way to reference the keybindings. For an interactive prompt, this would certainly be useful. I was thinking a toggleable help menu, for example what htop has:

I would be happy to try and tackle this, but any and all tips on how to get started in the codebase would be very helpful :)