🎨 feat(big-bear-runtipi): Update README with new app store details

This commit updates the README.md file to reflect the changes made to the Tipi App Store. The key changes are:

- The app store is now called "Big Bear Runtipi" and is maintained by BigBearTechWorld and the BigBearCommunity.
- The instructions for adding the app store to a Runtipi instance have been updated.
- The list of available apps has been updated to include a more comprehensive set of applications.

These changes aim to provide a more accurate and up-to-date information about the app store and the apps available for the Runtipi platform.