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/header.html

@@ -0,0 +1,19 @@
+<div class="headerContainer">
+  <div id="header_wrap" class="wrapper headerWrapper">
+    <div class="inner">
+      <img class="projectLogo" src="{{ '/static/logo.svg' | relative_url }}" alt="{{ site.title }}" title="{{ site.title }}" />
+      <h1 id="project_title">{{ site.title }}</h1>
+      <h2 id="project_tagline" class="fbossFontLight">{{ site.tagline }}</h2>
+
+      <section id="intro">
+        <p>{% if page.excerpt %}{{ page.excerpt | strip_html }}{% else %}{{ site.description }}{% endif %}</p>
+      </section>
+      <div id="promo" class="section promoSection">
+        {% for promo in site.data.promo %}
+          {% include plugins/{{promo.type}}.html button_href=promo.href button_text=promo.text %}
+          <div class="gridClear"></div>
+        {% endfor %}
+      </div>
+    </div>
+  </div>
+</div>