<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Timeliner</title>
</head>
<body class="">
   <div id="app"></div>
   <%= javascript_pack_tag 'iiif-timeliner' %>
</body>
</html>

<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Timeliner</title>
</head>
<body class="">
   <div id="app"></div>
   <%= javascript_pack_tag 'iiif-timeliner' %>
   <%= stylesheet_pack_tag 'iiif-timeliner' %>
</body>
</html>

Add missing stylesheet pack tag
Add missing stylesheet pack tag

Without this the CSS doesn't get included in production mode.