Post Gallery: Enqueues everything.

functions.php

<?php
add_action( 'post_gallery_enqueue', function() {
    // CSS
    wp_enqueue_style(
        'lightgallery', // Name / slug
        get_stylesheet_directory_uri() . '/node_modules/lightgallery/dist/css/lightgallery.min.css', // File location
        [], // Dependency
        '1.6.11' // Version
    );
    // js
    wp_enqueue_script(
        'lightgallery', // Name / slug
        get_stylesheet_directory_uri() . '/node_modules/lightgallery/dist/js/lightgallery-all.min.js', // File location
        ['jquery'], // Dependency
        '1.6.11' // Version
    );
    wp_enqueue_script(
        'lightbox-init', // Name / slug
        get_stylesheet_directory_uri() . '/js/lightbox-init.js', // File location
        ['lightgallery'], // Dependency
        '1.0.0' // Version
    );
} );