preact/index.html

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <title>FormValidation example - Integrate with Preact</title>

        <link
            rel="stylesheet"
            href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css"
        />
        <link
            rel="stylesheet"
            href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.3.1/css/bootstrap.min.css"
        />

        <!-- Replace with your path -->
        <link rel="stylesheet" href="/vendors/@form-validation/umd/styles/index.min.css" />

        <script src="https://npmcdn.com/preact@latest/dist/preact.js"></script>

        <!-- Replace with your path -->
        <script src="/vendors/@form-validation/umd/bundle/popular.min.js"></script>
        <script src="/vendors/@form-validation/umd/plugin-bootstrap/index.min.js"></script>

        <script src="DemoForm.js"></script>
    </head>
    <body>
        <div class="container">
            <div id="root"></div>
        </div>
        <script>
            preact.render(preact.createElement(DemoForm), document.getElementById('root'));
        </script>
    </body>
</html>