Filetreediff: expose it for users that have it enabled

We don't expose it to all the users yet, but we want to expose it for those that
we already enabled it on the Django Admin.

Requires readthedocs/readthedocs.org#11977

Author: humitos

readthedocsext/theme/templates/projects/addons_form.html

@@ -48,6 +48,10 @@
         <a class="item" data-tab="notifications">{% trans "Notifications" %}</a>
         <a class="item" data-tab="analytics">{% trans "Analytics" %}</a>
         <a class="item" data-tab="docdiff">{% trans "Visual diff" %}</a>
+        {# Only show File Tree Diff if it was previously enabled from Django Admin #}
+        {% if form.filetreediff_enabled %}
+          <a class="item" data-tab="filetreediff">{% trans "File tree diff" %}</a>
+        {% endif %}
         <a class="item" data-tab="link-previews">{% trans "Link previews" %}</a>
         <a class="item" data-tab="hotkeys">{% trans "Hotkeys" %}</a>
         <a class="item" data-tab="advanced">{% trans "Advanced" %}</a>
@@ -98,6 +102,15 @@
         </div>
       {% endblock addons_docdiff %}
 
+      {% block addons_filetreediff %}
+        {% if form.filetreediff_enabled %}
+          <div class="ui tab" data-tab="filetreediff">
+            {{ form.filetreediff_enabled | as_crispy_field }}
+            {{ form.filetreediff_ignored_files | as_crispy_field }}
+          </div>
+        {% endif %}
+      {% endblock addons_filetreediff %}
+
       {% block addons_link_previews %}
         <div class="ui tab" data-tab="link-previews">
           {{ form.linkpreviews_enabled | as_crispy_field }}