Updating Sitemap, according to @richardhinkamp's changes

Extension.php

@@ -41,15 +41,17 @@ public function sitemap($xml = false)
         $links = array(array('link' => $this->app['paths']['root'], 'title' => $this->app['config']->get('general/sitename')));
         foreach ( $this->app['config']->get('contenttypes') as $contenttype ) {
             if (!in_array($contenttype['slug'], $this->config['ignore_contenttype'])) {
+                $baseDepth = 0;
                 if (isset($contenttype['listing_template'])) {
-                    $links[] = array( 'link' => $this->app['paths']['root'].$contenttype['slug'], 'title' => $contenttype['name'] );
+                    $baseDepth = 1;
+                    $links[] = array( 'link' => $this->app['paths']['root'].$contenttype['slug'], 'title' => $contenttype['name'], 'depth' => 1 );
                 }
                 $content = $this->app['storage']->getContent(
                     $contenttype['slug'],
                     array('limit' => 10000, 'order' => 'datepublish desc')
                 );
                 foreach ($content as $entry) {
-                    $links[] = array('link' => $entry->link(), 'title' => $entry->getTitle(),
+                    $links[] = array('link' => $entry->link(), 'title' => $entry->getTitle(), 'depth' => $baseDepth + 1,
                         'lastmod' => date( \DateTime::W3C, strtotime($entry->get('datechanged'))));
                 }
             }

assets/_sitemap_list.tiwg

@@ -0,0 +1,23 @@
+<ul>
+{% set depth = 1 %}
+{% for entry in entries %}
+    {% if entry.link is defined %}
+        {% if entry.depth is defined and entry.depth > depth %}
+            <ul>
+        {% endif %}
+        {% if entry.depth is defined and entry.depth < depth %}
+            </ul>
+        {% endif %}
+        <li><a href="{{ entry.link }}">{{ entry.title }}</a></li>
+
+        {% if entry.depth is defined %}
+            {% set depth = entry.depth %}
+        {% else %}
+            {% set depth = 1 %}
+        {% endif %}
+    {% endif %}
+{% endfor %}
+{% if depth > 1 %}
+    </ul>
+{% endif %}
+</ul>

assets/sitemap.twig

@@ -13,5 +13,6 @@
         {% endif %}
     {% endfor %}
     </ul>
+    {% include 'assets/_sitemap_list.twig' %}
 </body>
 </html>