Add html_class block to base template
{% load i18n %}
{% load staticfiles %}
<!DOCTYPE html>
-<html lang="{{ LANGUAGE_CODE|default:"en-gb" }}" class="no-js">
+<html lang="{{ LANGUAGE_CODE|default:"en-gb" }}" class="{% block html_class %}no-js{% endblock %}">
<head>
<title>{% block title %}{{ shop_name }} - {{ shop_tagline }}{% endblock %}</title>
