index.html

<html>
  <head>
    <link rel="stylesheet" href="//spoppe-a.akamaihd.net/files/fabric/office-ui-fabric-core/5.0.1/css/fabric.min.css" />
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/react/15.4.2/react.js"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/react/15.4.2/react-dom.js"></script>
    <script type="text/javascript" src="dist/vendor.bundle.js"></script>

    <style>
    .ms-FocusRect {
      visibility: hidden;
    }

    .ms-Fabric.is-focusVisible .ms-Focusable:focus.ms-FocusRect,
    .ms-Fabric.is-focusVisible .ms-Focusable:focus .ms-FocusRect {
      visibility: visible;
    }
    </style>
  </head>
  <body>
    <script type="text/javascript" src="dist/main.bundle.js"></script>
  </body>
</html>