Include app js script to the template header

frontend/templates/funcs.go

@@ -10,6 +10,9 @@ func UseFuncs() template.FuncMap {
 		"sub": func(i int) int {
 			return i - 1
 		},
+		"getJSAppURL": func() string {
+			return URLJSApp
+		},
 		"getIndexURL": func() string {
 			return URLIndex
 		},

frontend/templates/head.go.tmpl

@@ -4,4 +4,6 @@
 
     <meta name="description" content="{{ .Description }}"/>
     <title>{{ .Title }}</title>
+
+    <script type="text/javascript" src="{{ getJSAppURL }}" async></script>
 </head>

frontend/templates/urls.go

@@ -5,4 +5,5 @@ const (
 	URLIndex = "/index.aspx"
 	URLBlog  = "/blog.aspx"
 	URLPost  = "/post.aspx"
+	URLJSApp = "/js-bin/app.js"
 )