[asciiarmor mode] Add to mode list

mode/index.html

@@ -85,6 +85,7 @@ option.</p>
       <li><a href="pascal/index.html">Pascal</a></li>
       <li><a href="pegjs/index.html">PEG.js</a></li>
       <li><a href="perl/index.html">Perl</a></li>
+      <li><a href="asciiarmor/index.html">PGP (ASCII armor)</a></li>
       <li><a href="php/index.html">PHP</a></li>
       <li><a href="pig/index.html">Pig Latin</a></li>
       <li><a href="properties/index.html">Properties files</a></li>