[Dock] Change background color based on active app and desktop

### Description of the new feature / enhancement

Could you please add a function that when I have windows on top, the dock of CmdPal will be black, and looks mixed with the system taskbar; when I am in the desk top, it become to transparent.(like the effect of translucentTB)
It will helps, thanks you a lot

### Scenario when this would be used?

When I am switching between desktop and window.

### Supporting information

The effect is similar with translucentTB

The request concerns the CmdPal dock and compares its desired effect with translucentTB, but it names no implementation files, tests, or entry points. Start by locating the CmdPal dock implementation and determine how desktop and active-window state are exposed; done means the dock changes between transparent on the desktop and black when windows are in front.

Written by the indexing model from the issue text.