Add StandardJS workflow

Been running these locally only.

examples/data-channels/jsfiddle/demo.js

@@ -1,17 +1,17 @@
 /* eslint-env browser */
 
-let pc = new RTCPeerConnection({
+const pc = new RTCPeerConnection({
   iceServers: [
     {
       urls: 'stun:stun.l.google.com:19302'
     }
   ]
 })
-let log = msg => {
+const log = msg => {
   document.getElementById('logs').innerHTML += msg + '<br>'
 }
 
-let sendChannel = pc.createDataChannel('foo')
+const sendChannel = pc.createDataChannel('foo')
 sendChannel.onclose = () => console.log('sendChannel has closed')
 sendChannel.onopen = () => console.log('sendChannel has opened')
 sendChannel.onmessage = e => log(`Message from DataChannel '${sendChannel.label}' payload '${e.data}'`)
@@ -27,7 +27,7 @@ pc.onnegotiationneeded = e =>
   pc.createOffer().then(d => pc.setLocalDescription(d)).catch(log)
 
 window.sendMessage = () => {
-  let message = document.getElementById('message').value
+  const message = document.getElementById('message').value
   if (message === '') {
     return alert('Message must not be empty')
   }
@@ -36,7 +36,7 @@ window.sendMessage = () => {
 }
 
 window.startSession = () => {
-  let sd = document.getElementById('remoteSessionDescription').value
+  const sd = document.getElementById('remoteSessionDescription').value
   if (sd === '') {
     return alert('Session Description must not be empty')
   }