chore(example): Fix url of TestLayout

Author: Masayuki Izumi

examples/1.html

@@ -52,7 +52,7 @@ <h3>React-Resizable Demo</h3>
     gives those components resize handles.
     </p>
     <p><a href="https://github.com/STRML/react-resizable">View project on GitHub</a></p>
-    <p><a href="https://github.com/STRML/react-resizable/blob/master/test/TestLayout.jsx">View this page's source</a></p>
+    <p><a href="https://github.com/STRML/react-resizable/blob/master/test/TestLayout.js">View this page's source</a></p>
     <div id="content"></div>
   </body>
 </html>