build/styleguide/index.html
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title><%=htmlWebpackPlugin.options.title%></title>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="https://unpkg.com/metro4/build/css/metro-all.css">
</head>
<body>
<div id="app"></div>
</body>
</html>