Add option to disable "prefix" pop-up (Pending Key Sequence)

[maxRN]

Currently when you configure a keybind with a prefix you get a "pending key sequence" pop up at the bottom of the terminal window:

I can see how it's helpful so you don't forget what mode you are in, but personally I find it a bit distracting and would like to disable it.

[oliver-cfc]

I find it distracting at the bottom because my cursor is normally at the bottom too so it covers the current line. I kind of like seeing it though so it would great if it could be configurable to be top/bottom/off.