Add experimental.datPeers Lab API

[pfrazee]

Demo video

Todos:

• Tests
• Publish 1.0.0 of https://github.com/beakerbrowser/dat-ephemeral-ext-msg

API:

// control the session data on your connection
experimental.datPeers.getSessionData()
experimental.datPeers.setSessionData(obj) // obj must be no larger than 255 bytes when JSONified

// manage connected peers
var peers = experimental.datPeers.list() // list all peers connected to the current page's dat
var peer  = experimental.datPeers.get(peerId)
await experimental.datPeers.broadcast(data) // send a message to all peers
experimental.datPeers.addEventListener('connect') // new peer
experimental.datPeers.addEventListener('disconnect') // peer closed connection
experimental.datPeers.addEventListener('message') // peer sent a message
experimental.datPeers.addEventListener('session-data') // peer set session data

// DatPeer object
peer.id
peer.sessionData
peer.send(data) // send a message to a peer

// all events:
event.peer // the sending DatPeer object

// message event:
event.message // string, object, or ArrayBuffer

[pfrazee]

Merged into draft-mode-rebased branch! I merged it manually because of the beaker/core refactor. Now draft-mode-rebased just needs to merge into master.