Add a p2p mini-hack

As a mobile developer, I want to complete a 20-30 mini-hack so that I can quickly understand the central concepts and basic techniques required to build a Couchbase Mobile p2p app.

Requirements:
- Simple peer discovery and authentication mechanism.
- Demonstrate use of filter functions to only replicate a subset of data.
- Demonstrate simple throttling to limit replication to one sync peer at a time.

No files, tests, or entry points are named. Start by locating the repository's existing Couchbase Mobile examples and peer-to-peer replication entry points, then determine how discovery, authentication, filtering, and throttling are demonstrated. Done means a runnable mini-hack covering all three listed requirements.

Written by the indexing model from the issue text.