Update examples index.

examples/index.html

@@ -13,10 +13,12 @@
       <li><a href="calendar/vix.html">calendar-vix</a></li>
       <li><a href="choropleth/choropleth.html">choropleth</a></li>
       <li><a href="chord/chord.html">chord</a></li>
+      <li><a href="contour/contour.html">contour</a></li>
       <li><a href="delaunay/delaunay.html">delaunay</a></li>
       <li><a href="donut/donut.html">donut</a></li>
       <li><a href="dot/dot.html">dot</a></li>
       <li><a href="force/force.html">force</a></li>
+      <li><a href="force/cluster.html">force-cluster</a></li>
       <li><a href="horizon/horizon.html">horizon</a></li>
       <li><a href="hull/hull.html">hull</a></li>
       <li><a href="line/line.html">line</a></li>