Add missing desktop clock properties to serializeBackground() function:
- desktopClock.scale
- desktopClock.position
- desktopClock.invertColors
- desktopClock.background.enabled
- desktopClock.background.opacity
- desktopClock.background.blur
- desktopClock.shadow.enabled
- desktopClock.shadow.opacity
- desktopClock.shadow.blur
This fixes the issue where the desktop clock background enabled toggle
(and other desktop clock settings) would not persist when the control
center was reloaded.