add gitbucket-backup-plugin

fixes #30

Author: McFoggy

index.html

@@ -149,7 +149,13 @@ <h2>
           </h2>
           <p>A GitBucket plugin that adds H2 console to the administration console.</p>
       </li>
-  </ul>
+      <li>
+        <h2>
+            <a class="post-link" href="https://github.com/jyuch/gitbucket-backup-plugin"><span class="fa fa-floppy-o"></span>Backup plugin</a>
+        </h2>
+        <p>Plugin providing backup functionnality for GitBucket</p>
+    </li>
+</ul>
     <p class="separator"/>
     <p>Your plugin is not listed here? You want to move your plugin under the organization? Please open a <a href="https://github.com/gitbucket-plugins/gitbucket-plugins.github.io/issues">ticket/issue</a> to reference your demand.</p>
 </div>