add websocket example

example/websocket/websocket.html

@@ -0,0 +1,9 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <title>emacs websocket test</title>
+    <script type="text/javascript" src="./websocket.js"></script>
+  </head>
+  <body></body>
+</html>