index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>React mapbox gl example</title>
    <meta charset="UTF-8">
    <meta name="description" content="React mapbox gl example">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/normalize/3.0.2/normalize.min.css">
    <style type="text/css">
      canvas {
        outline: none;
      }
    </style>
  </head>
  <body>
    <div id="root"></div>
    <script src="./bundle.js"></script>
  </body>
</html>