Let Light Switch change Office theme modes

### Description of the new feature / enhancement

Please consider adding optional Microsoft Office theme switching to PowerToys Light Switch.

Microsoft Office currently only supports automatic system-based switching between light and dark themes. It does not support switching from “Colorful” during the day to “Dark/Black” at night.

I would like Light Switch to optionally set Office themes like this:

Day: Office theme = Colorful
Night: Office theme = Dark/Black

### Scenario when this would be used?

Office theme switcher (Office 365) between Colorful to Dark/Black would make Light Switch much more useful for Microsoft 365 users who want automatic dark mode at night, but still need Office apps to be visually distinguishable during the day.

### Supporting information

_No response_

No files, tests, or entry points are identified. Start by locating Light Switch’s existing theme-switching implementation and determine how Office 365 theme settings could be changed. Done would mean an optional configuration that switches Office between Colorful during the day and Dark/Black at night.

Written by the indexing model from the issue text.