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/header_nav.html

@@ -0,0 +1,34 @@
+<div id="header_nav">
+  <div class="navSlideout">
+    <i class="menuExpand" id="header_nav_expander"><span></span><span></span><span></span></i>
+  </div>
+  <nav class="slidingNav">
+    <ul>
+      {% for item in site.data.nav %}
+      <li class="navItem">
+        {% if item.category == "external" %}
+          <a href="{{ item.href }}" target="_blank">{{ item.title }}</a>
+        {% else %}
+          <a href="{{ item.href | relative_url }}">{{ item.title }}</a>
+        {% endif %}
+      </li>
+      {% endfor %}
+      {% if site.searchconfig %}
+      {% include nav_search.html inputselector="search_input_react" %}
+      {% endif %}
+    </ul>
+  </nav>
+</div>
+<script>
+  var event = document.createEvent('Event');
+  event.initEvent('slide', true, true);
+  document.addEventListener('slide', function (e) {
+    document.body.classList.toggle('sliderActive');
+  }, false);
+  var headerNav = document.getElementById('header_nav');
+  var headerNavExpander = document.getElementById('header_nav_expander');
+  headerNavExpander.addEventListener('click', function(e) {
+    headerNav.classList.toggle('navSlideoutActive');
+    document.dispatchEvent(event);
+  }, false);
+</script>