Feature request: show UI indicator that run-or-raise is listening

[timcharper]

Nothing fancy, just a small window indicating that run-or-raise is listening because some prefix key was hit. Then hides on no match (maybe with a brief pause saying something to the effect that the key sequence had no match.

A main reason why this feature would be important is that run-or-raise consumes keypresses when a leader is invoked, and consumes the last non-matching keystroke.

Bonus: short a list of refining candidates that narrows as the key sequence progresses. For example, I have si for signal, sl for slack. If I forget a sequence, would be nice to have run-or-raise remind me a la nvim which-key.

[timcharper]

I've built a rust gtk app and I'm proficient in typescript, so I could contribute this, wanted to open a discussion before touching the code.

[e3rd]

I'd welcome any PR! The funcionality could be disablable in the settings so that everyone is satisfied :)