Add wayland index

Author: h-east

src/_layouts/vimdoc.html

@@ -222,6 +222,11 @@
 <li><a href="gui_x11.html">gui_x11</a></li>
 </ul></dd>
 
+<dt>System Integration</dt>
+<dd><ul>
+<li><a href="wayland.html">wayland</a></li>
+</ul></dd>
+
 <dt>Interfaces</dt>
 <dd><ul>
 <li><a href="if_cscop.html">if_cscop</a></li>