feat(admin): add custom favicon support Add favicon link to the head section of the default layout

- Use site_ico configuration or fallback to default favicon.ico

app/admin/view/layout/default.html

@@ -6,6 +6,7 @@
     <meta name="renderer" content="webkit">
     <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
     <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
+    <link rel="icon" href="{:sysConfig('site', 'site_ico')}" type="image/x-icon">
     <!--[if lt IE 9]>
     <script src="https://cdn.staticfile.org/html5shiv/r29/html5.min.js"></script>
     <script src="https://cdn.staticfile.org/respond.js/1.4.2/respond.min.js"></script>