html/background.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
    <meta
      http-equiv="Content-Security-Policy"
      content="default-src 'self'; frame-src 'self'; script-src 'self'; worker-src 'self';"
    />
    <link rel="stylesheet" href="../renderer/style.css" />
    <title>Set Background</title>
  </head>
  <body>
    <div id="container">
      <h1>Click on a background image to select</h1>
      <div id="bgImages">
        <button id="reset">Reset Background</button>
      </div>
    </div>
    <script src="../renderer/background.js"></script>
  </body>
</html>