add a basic default dark theme

templates/default_dark/file.html

@@ -0,0 +1,26 @@
+{% extends "base.html" %}
+
+{% block html_head_extra %}
+<link rel="stylesheet" type="text/css" href="syntax.css" />
+{% endblock html_head_extra %}
+
+{% block tab_files_selected -%}selected{% endblock -%}
+
+{% block subheader -%}
+<div class="breadcrumbs"><span class="site-title"><a href="{{ root_url | safe }}/index.html">{{site_name | default(value="Itsy-Gitsy") }}</a></span>{% if name -%}&nbsp;&gt;&gt;&nbsp;<span class="site-title">{{ name }}</span>{% endif -%}&nbsp;&gt;&gt;&nbsp;<span class="repo-name">{{ file.path }}</span></div>
+{% endblock -%}
+
+{% block content %}
+<div class="nocap-header file">{{ file.path }}</div>
+<div class="file-contents">
+{% if file.contents_safe -%}
+{% if file.contents_preformatted -%}
+<pre>{{file.contents | safe }}</pre>
+{%- else -%}
+{{file.contents | safe }}
+{%- endif -%}
+{%- else -%}
+<pre style="margin: 0">{{file.contents}}</pre>
+{%- endif -%}
+</div>
+{% endblock content %}