constructor(url, opts) {
    if (isBrowser) this.storage = new CrossStorageClient(url, opts)
  }
Constructs a new cross storage client
@param {string} url    The url to a cross storage hub
@param {object} [opts] An optional object containing additional options
@param {object} [opts.timeout] timeout
@param {object} [opts.frameId] frameId
@example
const storage = new RemoteStorage('https://example.com/storage.html')
@example
const storage = new RemoteStorage('https://example.com/storage.html', {
  timeout: 5000,
  frameId: 'storageFrame'
})