Update readme

www/video-stream.js

@@ -1,5 +1,9 @@
 import {VideoRTC} from './video-rtc.js';
 
+/**
+ * This is example, how you can extend VideoRTC player for your app.
+ * Also you can check this example: https://github.com/AlexxIT/WebRTC
+ */
 class VideoStream extends VideoRTC {
     set divMode(value) {
         this.querySelector('.mode').innerText = value;