Description

Apply dynamic dark/light mode when changing broswer's appearance theme

Testing Instructions

1. Pull and checkout the branch enhancement/dynamic-dark-mode
2. Build and run the extension: npm run build:all && npm run dev:ext
3. Open Privacy Sandbox tab on DevTools
4. Go tochrome://settings/appearance
5. Select a different appearance theme mode
6. Observe: the PSAT extension swaps theme mode automatically

Checklist

• I have thoroughly tested this code to the best of my abilities.
• I have reviewed the code myself before requesting a review.
• This code is covered by unit tests to verify that it works as intended.
• The QA of this PR is done by a member of the QA team (to be checked by QA).