Allow page background uisng @page rule

Expects black page with white text

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>page-background.html</title>
    <style>
        @page {
            size: 200px 100px;
            margin: 10px;
            background: black;
        }

        html {
            color: white;
        }
    </style>
</head>
<body>
    hello world
</body>
</html>

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