add links to package manager on download page

doc/index.html

@@ -86,6 +86,8 @@
             <li><a href="http://nodejs.org/dist/v0.6.6">Other release files</a></li>
             <li><a href="https://raw.github.com/joyent/node/v0.6.6/LICENSE">License</a></li>
             <li><a href="https://github.com/joyent/node">Git Repository</a></li>
+            <li><a href="https://github.com/joyent/node/wiki/Installing-Node.js-via-package-manager">Installing
+            with a Package Manager</a>
         </ul>
     </div>