Feat: Implement ThemeListener for winui3

[HO-COOH]

Fixes

Closes #135

PR Type

What kind of change does this PR introduce?

Bugfix

What is the current behavior?

It does not work under WinUI3.

What is the new behavior?

This PR implements the broken ThemeListener, closes #135. I really need a working ThemeListener for handling Dark/Light theme changes. I am not concerned with HighContrast at the time being.

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• [x] Based off latest main branch of toolkit
• [x] Tested code with current supported SDKs
• [x] Tests for the changes have been added (if applicable)
• [x] Header has been added to all new source files
• [x] Contains NO breaking changes

Other information