Add default templates, styles, and scripts for documentation site

docs-gen/defaults/templates/portal.html

@@ -0,0 +1,12 @@
+{% extends "base.html" %}
+
+{% block layout_class %}no-sidebar{% endblock %}
+
+{% block body %}
+<main class="content portal">
+  <article>
+    <h1>{{ page.title }}</h1>
+    {{ content | safe }}
+  </article>
+</main>
+{% endblock %}