add_filter("the_content", "learndash_course_grid_css");
function learndash_course_grid_css( $content ) {
    if (
           strpos( $content, "[ld_course_list" ) === false
        && strpos( $content, "[ld_lesson_list" ) === false
        && strpos( $content, "[ld_quiz_list" )   === false
        && strpos( $content, "[ld_topic_list" )  === false
    ) {
        return $content;
    }

    wp_enqueue_style( 'learndash_course_grid_css', plugins_url( 'style.css', __FILE__ ) );
    wp_enqueue_script( 'learndash_course_grid_js', plugins_url( 'script.js', __FILE__ ), array('jquery' ) );
    wp_enqueue_style( 'ld-cga-bootstrap', plugins_url( 'bootstrap.min.css', __FILE__ ) );

    return preg_replace( '/(.*\[ld_\w+_list.*)/', '<div id="ld_course_list">$1</div>', $content );
}