add_filter('site-reviews/review/build/after', function (array $tags, Review $review) {
    $videoUrl = $review->custom->video_url;
    if (!empty($videoUrl)) {
        $tags['video_url'] = sprintf('<iframe src="%s" frameborder="0" allowfullscreen></iframe>');
    }
    return $tags;
}, 20, 2);