Add link to knight code.

3d/index.html

@@ -124,6 +124,7 @@ <h1>Liz Learns 3D</h1>
         <p>A car using basic geometries in three.js and a moving pointlight.</p>
         <p>The front car light was inspired by the show Knight Rider.</p>
       </a>
+      <a href="https://github.com/lizlam/knight">{code}</a>
     </div>
   </main>
 </body>