'powered by pretix' link

src/pretix/presale/static/pretixpresale/less/main.less

@@ -4,3 +4,9 @@
 
 @import "event.less";
 @import "forms.less";
+
+footer {
+    text-align: center;
+    padding: 10px 0;
+    font-size: 11px;
+}

src/pretix/presale/templates/pretixpresale/event/base.html

@@ -28,5 +28,12 @@
     {% block content %}
     {% endblock %}
 </div>
+<footer>
+    {% with "href='http://pretix.eu'" as a_attr %}
+        {% blocktrans trimmed %}
+            powered by <a {{ a_attr }}>pretix</a>
+        {% endblocktrans %}
+    {% endwith %}
+</footer>
 </body>
 </html>