better header/footer template, add syntax highlighting

templates/repos.html

@@ -1,3 +1,7 @@
+{% extends "base.html" %}
+
+{% block content %}
 {% for repo in repos | sort(attribute="name") -%}
 <a href="{{repo.name}}/summary.html">{{ repo.name }}</a> ({{repo.metadata.website}}) [{{repo.metadata.attributes | get(key="some_extra_thing", default="")}}] ({{ts_to_date(ts=repo.history[0].ts_utc, tz=repo.history[0].ts_offset)}})<br/>
 {% endfor -%}
+{% endblock content %}