Dynamically add WooCommerce product categories to primary menu

functions.php

<?php

function gp_add_woo_categories_to_menu($items, $args)
{
	if ($args->theme_location == 'primary') {

		$cat_args = array(
			'orderby'    => 'name',
			'order'      => 'asc',
			'hide_empty' => true,
		);

		$product_categories = get_terms('product_cat', $cat_args);

		$menu_item = '<li class="menu-item">';
		$menu_item .= '<a>' . __('Categories', 'generatepress') . '</a>';
		$menu_item .= '<ul class="sub-menu">';
		foreach ($product_categories as $category) {
			$menu_item .= '<li class="menu-item">';
			$menu_item .= '<a href="' . get_category_link($category->term_id) . '">';
			$menu_item .= $category->name;
			$menu_item .= '</a>';
			$menu_item .= '</li>';
		}
		$menu_item .= '</ul>';
		$menu_item .= '</li>';
		$items .= $menu_item;
	}
	return $items;
}
add_filter('wp_nav_menu_items', 'gp_add_woo_categories_to_menu', 10, 2);