message: open returns `this`
  closes
diff: @@ -90,7 +90,7 @@ export class UserMedia extends ToneAudioNode<UserMediaOptions> {
  * With no argument, the default stream is opened.
  * @return The promise is resolved when the stream is open.
  */
  - async open(labelOrId?: string | number): Promise<void> {
  + async open(labelOrId?: string | number): Promise<this> {
  this.assert(UserMedia.supported, "UserMedia is not supported");
  // close the previous stream
  if (this.state === "started") {
  @@ -132,6 +132,7 @@ export class UserMedia extends ToneAudioNode<UserMediaOptions> {
  connect(mediaStreamNode, this.output);
  this._mediaStream = mediaStreamNode;
  }
  + return this;
  }
  /**
  