Adds a "Featured" flash to featured WooCommerce products (like a sale flash)

wc-add-featured-flash.php

function wc_add_featured_product_flash() {
	global $product;

	if ( $product->is_featured() ) {
		echo '<span class="onsale">Featured</span>';
	}
}
add_action( 'woocommerce_before_shop_loop_item_title', 'wc_add_featured_product_flash' );
add_action( 'woocommerce_before_single_product_summary', 'wc_add_featured_product_flash' );