Add meta viewport tag for scale (for phones)

src/assets/index.html

@@ -2,9 +2,10 @@
   <head>
     <title>{app_title}</title>
     <meta content="text/html;charset=utf-8" http-equiv="Content-Type" />
+    <meta name="viewport" content="width=device-width, initial-scale=1">
     <meta charset="UTF-8" />
     {style_include}
-    
+
   </head>
   <body>
     <div id="main"></div>