v6.0.0

• Breaking: the SignalProtocolRelayServer contract requires the relay
  connection state. SignalProtocolClient gains the relayConnectionState
  getter and subscribeRelayConnectionState(listener), which returns an
  Unsubscribe. The RelayConnectionState type has a state (stopped,
  connecting, connected, or reconnecting), a since time, and on
  reconnecting a reason (handshake, protocol, closed, error,
  frame, authentication, or silent). The reason names the site that
  failed, never an error message. The state reads stopped before
  startRelaySubscription() and after stopRelaySubscription(). A token
  renewal emits nothing unless its new socket fails, and the same value never
  emits twice. SignalProtocolRelayServer requires both members, so a custom
  adapter must implement them. The memory and Convex adapters report
  connected and stopped only. The state is local to this device and is not
  presence.

• New: useRelayConnectionState and useRelayLifecycle hooks, and
  bindRelayLifecycle. useRelayConnectionState({ signal }) gives the
  state to a component for a local indicator. bindRelayLifecycle(signal, appState, { keepOpenInBackground }) from ./client takes an object with the
  shape of React Native's AppState, so the client entry imports no
  react-native. useRelayLifecycle({ signal, keepOpenInBackground }) from
  ./hooks passes AppState to it and does nothing on web.

• Behavior change: the lifecycle binding closes the socket in the
  background. With bindRelayLifecycle or useRelayLifecycle, background
  calls stopRelaySubscription(), which closes the socket with code 1000.
  active starts the subscription again after that stop, and the Relay
  replays retained messages over the new socket. inactive changes nothing,
  and there is no grace delay. A stop that the app made stays in effect.
  keepOpenInBackground: true keeps the socket open, for example while an
  Android foreground service runs.

• Behavior change: the hosted subscription gives up on a silent socket at
  60 s. The ping watchdog reconnects 60 s after the open or after the last
  answered ping, not 90 s. The Relay closes a silent socket at 75 s, so the
  client now gives up first.