theme.php
<!DOCTYPE html>
<html>
<head>
<?=\Lia\Addon\Resources::from($lia)->getHtml();?>
</head>
<body>
<header>
</header>
<main>
<?=\Lia\Addon\View::from($lia)->view('error/header');?>
<?=$content?>
</main>
<footer>
</footer>
</body>
</html>