wp-duckbehaviorjournal/footer.php

<!-- Footer -->
<footer class="bg-light py-4">
    <div class="container text-center">
        <p><?php echo get_theme_mod('footer_text', '&copy; ' . date('Y') . ' Duck Behavior Journal. All rights reserved.'); ?></p>
        <div>
            <?php
            wp_nav_menu(array(
                'theme_location' => 'footer',
                'menu_class'     => 'nav justify-content-center',
                'container'      => false,
                'depth'          => 1,
            ));
            ?>
        </div>
        <div class="social-media mt-3">
            <?php if (get_theme_mod('footer_facebook_link')) : ?>
                <a href="<?php echo get_theme_mod('footer_facebook_link'); ?>" class="mx-2"><img src="<?php echo get_template_directory_uri(); ?>/facebook-icon.png" alt="Facebook"></a>
            <?php endif;
            if (get_theme_mod('footer_twitter_link')) : ?>
                <a href="<?php echo get_theme_mod('footer_twitter_link'); ?>" class="mx-2"><img src="<?php echo get_template_directory_uri(); ?>/twitter-icon.png" alt="Twitter"></a>
            <?php endif;
            if (get_theme_mod('footer_linkedin_link')) : ?>
                <a href="<?php echo get_theme_mod('footer_linkedin_link'); ?>" class="mx-2"><img src="<?php echo get_template_directory_uri(); ?>/linkedin-icon.png" alt="LinkedIn"></a>
            <?php endif; ?>
        </div>
    </div>
</footer>

<div id="lightbox" class="lightbox">
    <span class="lightbox-close">&times;</span>
    <img class="lightbox-content" id="lightbox-img">
</div>

<?php wp_footer(); ?>
</body>

</html>