[docs/feather] Add S99 to syn_index.html

It's already available if you type the URL directly, this just makes it
accessible from the index.

docs/feather/syn_index.html

@@ -377,6 +377,14 @@ <h2><a name="Feather">Official Perl 6 Documentation</a></h2>
 	<td></td>
     </tr>
     <tr><td>33</td><td>Diagnostic messages</td><td colspan="4">(TBD)</td></tr>
+    <tr>
+        <td>99</td>
+        <td>Glossary</td>
+        <td><a href="S99.html"><strong>Synopsis</strong></a></td>
+        <td><a href="http://raw.github.com/perl6/specs/master/S99-glossary.pod">S99-glossary.pod</a></td>
+        <td></td>
+        <td></td>
+    </tr>
 </table>
 
 <h3>Indexes</h3>