Power Display: keyboard brightness buttons to control brightness of the display based on mouse pointer position

Nobody has claimed this yet.

### Description of the new feature / enhancement

An option that changes the behaviour of the keyboard brightness + / - buttons to no longer affect exclusively the primary display. Instead, it would affect the display where the mouse pointer currently resides in.

### Scenario when this would be used?

If I had multiple monitors, every time where I would want to change the brightness of one of those displays, I would have to move the mouse to the Power Display menu, and change the brightness of the corresponding monitor from there.

But with this feature, I would be able to just have my mouse positioned in the display who's brightness I want to switch, and have the brightness buttons on my keyboard affect this display in particular. In my opinion it feels like the natural behaviour of the brightness keys should function.

### Supporting information

This feature exists already in some MacOS display brightness apps (namely [BetterDisplay](https://betterdisplay.pro/)), and it's on by default.
It basically allows for defining the behavior of the brightness keys to be either: **Screen with mouse pointer**, **Screen with window in focus** or **All suitable screens**.

The issue names no files, tests, or entry points. Start by locating Power Display's keyboard brightness handling and monitor-selection logic, then determine how pointer position identifies a display. Done means an option can select the pointer's display for brightness changes without affecting other displays.

Written by the indexing model from the issue text.