packages/shell-chrome/devtools.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title></title>
    <style>
      html, body {
        height: 100%;
      }
      #container {
        display: flex;
        height: 100%;
      }
    </style>
  </head>
  <body>
    <div id="container">
      <div id="app"></div>
    </div>

    <script src="./build/devtools.js"></script>
  </body>
</html>