Add examples/play-from-disk

Using IVFReader demonstrate how users can stream a video
from hard disk to browser.

Relates to #636

examples/play-from-disk/jsfiddle/demo.js

@@ -0,0 +1,39 @@
+/* eslint-env browser */
+
+let pc = new RTCPeerConnection()
+let log = msg => {
+  document.getElementById('div').innerHTML += msg + '<br>'
+}
+
+pc.ontrack = function (event) {
+  var el = document.createElement(event.track.kind)
+  el.srcObject = event.streams[0]
+  el.autoplay = true
+  el.controls = true
+
+  document.getElementById('remoteVideos').appendChild(el)
+}
+
+pc.oniceconnectionstatechange = e => log(pc.iceConnectionState)
+pc.onicecandidate = event => {
+  if (event.candidate === null) {
+    document.getElementById('localSessionDescription').value = btoa(JSON.stringify(pc.localDescription))
+  }
+}
+
+// Offer to receive 1 audio, and 2 video tracks
+pc.addTransceiver('video', {'direction': 'sendrecv'})
+pc.createOffer().then(d => pc.setLocalDescription(d)).catch(log)
+
+window.startSession = () => {
+  let sd = document.getElementById('remoteSessionDescription').value
+  if (sd === '') {
+    return alert('Session Description must not be empty')
+  }
+
+  try {
+    pc.setRemoteDescription(new RTCSessionDescription(JSON.parse(atob(sd))))
+  } catch (e) {
+    alert(e)
+  }
+}