Add Explore groups to apps & shortcuts

Context / Problem: Currently, the "Explore groups" option is hard to find in the app. Users who want to discover and join groups often don't know it exists, so they miss out on groups that are relevant to them.

Desired solution: A more prominent, easy-to-find entry point for "Explore groups", for example:
- The ability for admins to add an "Explore groups" button or tile to the hub