Add endpoint/method to force broadcast/search for local textile peers

libp2p has pretty good mdns findability... so it would be nice to have an API endpoint that forces the peer to announce and search for peers locally. could be useful for testing with local peers, but also for pairing, sharing between friends physically co-located, etc From a conversation on Slack: libp2p may not provide an event for when a peer connects, but we could poll for changes that look like textile peers.