Include admin.css in OIDC admin pages

Author: cicnavi

templates/base.twig

@@ -6,6 +6,7 @@
 {% extends "base.twig" %}
 
 {% block preload %}
+    <link rel="stylesheet" href="{{ asset('css/admin.css', 'admin') }}">
     <link rel="stylesheet" href="{{ asset('css/src/default.css', 'oidc') }}">
 {% endblock %}