HTMLはこうなって
<body>
<div id="root">
</div>
<div id="root2">
</div>
<!-- scripts -->
<script src="./dist/app-bundle.js"></script>
</body>
<body>
<div id="root">
</div>
<div id="root2">
</div>
<!-- scripts -->
<script src="./dist/app-bundle.js"></script>
</body>