Properly wait for the serviceworker to be ready

It seems that there is a small wait between when the .ready method is called and the serviceworker actually claims the client.

We should wait for the controller before firing ready:

  navigator.serviceWorker.register('/worker.js').then(function () {
    return navigator.serviceWorker.ready
  }).then(function (reg) {
    if (navigator.serviceWorker.controller) {
      self.emit('ready')
    } else {
      var listener = navigator.serviceWorker.addEventListener('controllerchange', () => {
        navigator.serviceWorker.removeEventListener('controllerchange', listener)
        self.emit('ready')
      })
    }
  })

Start by locating the service-worker registration and the handling of navigator.serviceWorker.ready described in the issue. Ensure the ready event is emitted only after navigator.serviceWorker.controller is available, including the controllerchange path, and verify the registration behavior in the browser.