all image gradient

add_action('wp_footer', function () {
    ?>
    <script>
        document.addEventListener("DOMContentLoaded", function () {
            (function(){
                document.querySelectorAll('.thumbnail-container>img').forEach(function(value){
                    var container = document.createElement('div');
                    container.classList.add('jeg_thumbnail_cover');
                    container.style.width = '100%';
                    container.style.height = '100%';
                    container.style.position = 'absolute';
                    container.style.background = 'linear-gradient(353deg, rgba(0, 0, 0, 0.57), transparent)';
                    value.after(container);
                });
            })()
        });
    </script>
    <?php
}, 99999);