add latest new section to frontpage

We use a custom override template (jinja) to generate a suitable list of
new items.

Also added first text for announcing our new user docs

overrides/frontpage.html

@@ -0,0 +1,18 @@
+{% extends "base.html" %}
+
+{% block content %}
+{{ super() }}
+
+<!-- latest news requires that we have the blog plugin configured! -->
+{% if pages %}
+<h2 id="latest-news">Latest News</h2>
+<ul class="frontpage_style">
+  {# we only capture the two newest entries #}
+  {% for file in (pages | selectattr('page.meta.date') | sort(attribute='page.meta.date.created', reverse=true))[:2] %}
+  <li><a href="{{ file.dest_uri }}">{{ file.page.title }}</a> &ndash; <time datetime="{{ file.page.meta.date.created }}"> {{- file.page.meta.date.created | date -}}</time></li>
+  {% endfor %}
+</ul>
+{# TODO we should try using the pages object to always get the correct relative uri #}
+<p>&rarr; See <a href="/news/index.html">News</a> for more...</p>
+{% endif %}
+{% endblock %}