[assets] fix the loading of the manifest.json

It is generated dynamically, and as such can not be served by the cdn.

Signed-off-by: Jakob Ackermann <[email protected]>

Author: das7pad

templates/base/head.tmpl

@@ -5,7 +5,7 @@
 	<meta name="viewport" content="width=device-width, initial-scale=1">
 	<meta http-equiv="x-ua-compatible" content="ie=edge">
 	<title>{{if .Title}}{{.Title}} - {{end}} {{if .Repository.Name}}{{.Repository.Name}} - {{end}}{{AppName}}</title>
-	<link rel="manifest" href="{{StaticUrlPrefix}}/manifest.json" crossorigin="use-credentials">
+	<link rel="manifest" href="{{AppSubUrl}}/manifest.json" crossorigin="use-credentials">
 
 	<script>
 		if ('serviceWorker' in navigator) {