function add_custom_script_to_footer() {
    ?>
    <script>
        let slideIndex = 1;
        showSlides(slideIndex);

        // Next/previous controls
        function plusSlides(n) {
            showSlides(slideIndex += n);
        }

        // Thumbnail image controls
        function currentSlide(n) {
            showSlides(slideIndex = n);
        }

        function showSlides(n) {
            let i;
            let slides = document.getElementsByClassName("mySlides");
            let dots = document.getElementsByClassName("dot");
            if (n > slides.length) {
                slideIndex = 1;
            }
            if (n < 1) {
                slideIndex = slides.length;
            }
            for (i = 0; i < slides.length; i++) {
                slides[i].style.display = "none";
            }
            for (i = 0; i < dots.length; i++) {
                dots[i].className = dots[i].className.replace(" active", "");
            }
            slides[slideIndex - 1].style.display = "block";
            dots[slideIndex - 1].className += " active";
        }
    </script>
    <?php
}
add_action( 'wp_footer', 'add_custom_script_to_footer' );
