feat: Get plugin working with Joyce Geometry Applets as well

Since third-party code may not be loaded from the web in an extension,
  requires bundling many GeoGebra app files into the extension.

  Still to come: control panel for the extension.

public/index.html

@@ -10,6 +10,7 @@
       <li> <a href="inscribed-equilateral.html">Before</a> </li>
       <li> <a href="inscribed-revived.html">Revived</a> </li>
       <li> <a href="inscribed-modified.html">After</a> </li>
+      <li> <a href="jelts/book1/joyceDefI2.html">Book I Def 2</a> </li>
     </ul>
     <h2>WRL Files</h2>
     <ul><li> <a href="wrl_2.html">Target two</a></li>