Mouse scroll outputs for keyboard manager

### Description of the new feature / enhancement

I would very much appreciate being able to bind keys to mouse scroll events, preferably in all four directions and with separate hotkeys for different distances. I'm not sure whether this would be best placed in the Keyboard Manager or as a new feature.

### Scenario when this would be used?

Any time someone is trying to use a computer without a mouse and simply needs to scroll. Up/down arrow keys only work a minority of the time, as I find that my cursor is in a text box or the app / site I'm in has bound their own actions to the arrow keys.

### Supporting information

When trying to use a computer without a mouse, one of the continued pain points is scrolling. There are many tools that allow me to move the mouse but few to none that allow me to simply scroll the focused window. I am left manually moving the mouse cursor over to the scroll bar to click and then moving it back again, which is very tedious.

The issue points to Keyboard Manager; start by locating that component and reviewing how it currently defines keyboard bindings and sends input. Clarify the supported scroll directions, distances, focused-window behavior, and configuration flow. Done means users can bind keys to four-direction scroll events with distinct distances.

Written by the indexing model from the issue text.