- doc index

git-svn-id: http://root.cern.ch/svn/root/trunk@21457 27541ba8-7e3a-0410-8455-c3a389f83636

g3d/doc/index.txt

+This directory contains the basic 3D classes.
+BEGIN_HTML
+<ul>
+<li><a href="http://root.cern.ch/root/htmldoc/examples/shapes.C.html">Shapes.</a></li>
+<li><a href="http://root.cern.ch/root/htmldoc/examples/tornado.C.html">TPolyMarker3D example.</a></li>
+</ul>
+END_HTML