Trigger elm-reactor build before loading elm.js

index.html

<script>
    var img = new Image();
    img.onerror = function () {
      var script = document.createElement('script');
      script.src = 'elm.js';
      script.onload = function () {
        Elm.fullscreen(Elm.Main, {
          locationHash: window.location.hash,
          windowDimensions: [window.innerWidth, window.innerHeight]
        })
      }
      document.documentElement.appendChild(script);
    }
    img.src = 'Main.elm';
</script>