Screen backlight change notification should appear on the affected screen

[tintou]

Prerequisites

• I have searched open and closed issues for duplicates.

Feature

Is your feature request related to a problem? Please describe.
I have a laptop with an external monitor and when I work the external monitor is my primary output. When I press the "decrease/increase backlight level" key on the keyboard, I see the light increasing on my laptop but the notification is on my external monitor which remains unaffected.

Describe the solution you'd like
Show the backlight level notification on the screen that is actually changing its level

Existing work
N/A

Describe alternatives you've considered
N/A

Additional context
N/A