pie.html

<footer th:fragment="pie" class="px-2 py-2 fixed-bottom bg-dark" xmlns:th="http://www.w3.org/1999/xhtml">
    <span class="text-muted">Sistema de ventas Spring Boot
        <i class="fa fa-code"></i>
        con
        <i class="fa fa-heart"></i>
        por
        <a class="text-white" href="//parzibyte.me/blog">Parzibyte</a>
    </span>
    <script type="text/javascript">
        // Tomado de https://github.com/parzibyte/cotizaciones_web/blob/master/js/cotizaciones.js#L2
        document.addEventListener("DOMContentLoaded", () => {
            const menu = document.querySelector("#menu"),
                botonMenu = document.querySelector("#botonMenu");
            if (menu) {
                botonMenu.addEventListener("click", () => menu.classList.toggle("show"));
            }
        });
    </script>
</footer>