Added base structure for xychart

demos/index.html

@@ -60,6 +60,9 @@
       <li>
         <h2><a href="./quadrantchart.html">Quadrant charts</a></h2>
       </li>
+      <li>
+        <h2><a href="./xychart.html">XY charts</a></h2>
+      </li>
       <li>
         <h2><a href="./requirements.html">Requirements</a></h2>
       </li>