A tiny in memory replicated key value store that syncs via an iroh-gossip topic.
The store provides a two level map, where the first level is a scope (a PublicKey) and the second level is an arbitrary Bytes key. Values are Bytes, but come with a timestamp.
Values contain a signature over (key, value, timestamp) so they
can be replicated.
The store can be observed, with filters on scope, key and timestamp.