Add li option

_includes/directory-tree.html

@@ -9,13 +9,15 @@
 
 Parameters that can be passed as include or Front Matter directory-tree hash:
 
+  li          The generated tree is a list item. Do not wrap an <ul> tag around it.
+
   dir_class   Add a class attribute with the specified classes to <li> tags of all directories.
               If not set, wrap a <strong> tag around titles of all directories.
 
   strong      Wrap a <strong> tag around titles of the pages that have `strong: true` in the Front Matter.
               Default: false.
 {%- endcomment -%}
-<ul>
+{%- unless include.li or page.directory-tree.li %}<ul>{%- endunless %}
   {%- if include.dir_class -%}
     {%- assign dir_li = '<li class="' | append:  include.dir_class | append: '">' -%}
   {%- else -%}
@@ -111,4 +113,4 @@
     </ul>
   </li>
   {%- endfor %}
-</ul>
+{% unless include.li or page.directory-tree.li -%}</ul>{%- endunless %}

_layouts/doc.html

@@ -109,6 +109,7 @@
 
 			{% include directory-tree.html
 				dir="/doc/modules"
+				li=true
 				strong=true
 				dir_class="r-docs-subnav list-group-item" %}