def html(filename='index.html'):
    """
    Returns a simple HTML5 template.
    """
    with open(filename, 'w') as f:
        f.write(
            """<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>

</body>
</html>"""
            )
