Use correct syntax for viewport meta tag

src/index.ejs

@@ -2,7 +2,7 @@
 <html>
   <head>
     <meta charset="UTF-8">
-    <meta name="viewport" content="width=device-width; initial-scale=1">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
     <title><%= htmlWebpackPlugin.options.title %></title>
   </head>
   <body>