euscan: add basic overlay support

Signed-off-by: Corentin Chary <corentincj@iksaif.net>

euscanwww/templates/euscan/overlay.html

@@ -0,0 +1,12 @@
+{% extends "euscan/_datatable.html" %}
+
+{% load packages %}
+
+{% block title %}
+{{ block.super }} - Overlay: {{ overlay }}
+{% endblock %}
+
+{% block content %}
+<h2>Overlay: {{ overlay }}</h2>
+{% packages packages %}
+{% endblock %}