Move yoga docs into docs folder on master branch

Summary: Move yoga docs into master branch so that pull requests are able to include doc updates as part of other changes.

Reviewed By: JoelMarcey

Differential Revision: D4365700

fbshipit-source-id: 2f46a88974104c454c00bcdf1257abb5c4075a68

docs/_includes/nav/collection_nav_group.html

@@ -0,0 +1,19 @@
+<div class="navGroup navGroupActive navGroupCurrent">
+  <h3><span>{{ grouptitle }}</span></h3>
+  <ul>
+    {% if include.data_collection %}
+      {% for item in group.items %}
+        {% for collectionitem in include.data_collection %}
+        {% if collectionitem.docid == item.id %}
+          {% assign groupitem = collectionitem %}
+          {% include nav/collection_nav_group_item.html %}
+        {% endif %}
+        {% endfor %}
+      {% endfor %}
+    {% else %}
+      {% for groupitem in groupitems %}
+      {% include nav/collection_nav_group_item.html %}
+      {% endfor %}
+    {% endif %}
+  </ul>
+</div>