function isEstablished (ws) {
  // If the server's response is validated as provided for above, it is
  // said that _The WebSocket Connection is Established_ and that the
  // WebSocket Connection is in the OPEN state.
  return ws[kReadyState] === states.OPEN
}
@see https://dom.spec.whatwg.org/#concept-event-fire
@param {string} e
@param {EventTarget} target
@param {EventInit | undefined} eventInitDict