Add HaxPad to real-world uses

doc/realworld.html

@@ -43,6 +43,7 @@
       <li><a href="https://github.com/github/android">GitHub's Android app</a></li>
       <li><a href="https://script.google.com/">Google Apps Script</a></li>
       <li><a href="http://try.haxe.org">Haxe</a> (Haxe Playground) </li>
+      <li><a href="http://haxpad.com/">HaxPad</a> (editor for Win RT)</li>
       <li><a href="http://megafonweblab.github.com/histone-javascript/">Histone template engine playground</a></li>
       <li><a href="http://icecoder.net">ICEcoder</a> (web IDE)</li>
       <li><a href="http://extensions.joomla.org/extensions/edition/editors/8723">Joomla plugin</a></li>