Adds a button to the theme selector to help people find more themes in
the extension store.

![CleanShot 2025-02-04 at 09 00
20@2x](https://github.com/user-attachments/assets/fd430ff5-b0e3-4be0-ac4a-eeaf0093089b)

Release Notes:

- Added a way to access the extension store from the theme selector to
make it easier to find new themes.