Refactors style bundling so it's easy to avoid an insecure CSP

_includes/postslist.njk

@@ -1,4 +1,5 @@
-<ol reversed class="postlist" style="counter-reset: start-from {{ (postslistCounter or postslist.length) + 1 }}">
+{%- css %}.postlist { counter-reset: start-from {{ (postslistCounter or postslist.length) + 1 }} }{% endcss %}
+<ol reversed class="postlist">
 {% for post in postslist | reverse %}
 	<li class="postlist-item{% if post.url == url %} postlist-item-active{% endif %}">
 		<a href="{{ post.url }}" class="postlist-link">{% if post.data.title %}{{ post.data.title }}{% else %}<code>{{ post.url }}</code>{% endif %}</a>