Add doc for unhooking/removing WooCommerce email notifications snippet. (#39280)

* add doc for unhooking/removing WooCommerce email notifications.

* Update snippet to follow snippet standards.

Co-authored-by: Niels Lange <info@nielslange.de>

* Update docs/snippets/unhook--remove-woocommerce-emails.md

Co-authored-by: Niels Lange <info@nielslange.de>

---------

Co-authored-by: Niels Lange <info@nielslange.de>

docs/snippets/README.md

@@ -2,4 +2,5 @@
 
 Various code snippets you can add to your site to enable custom functionality:
 
--   [Add a message above the login / register form](./before-login--register-form.md)
+- [Unhook and remove WooCommerce emails](./unhook--remove-woocommerce-emails.md);
+- [Add a message above the login / register form](./before-login--register-form.md)

docs/snippets/unhook--remove-woocommerce-emails.md

@@ -0,0 +1,45 @@
+# Unhook and remove WooCommerce emails
+
+> This is a **Developer level** doc. If you are unfamiliar with code and resolving potential conflicts, select a [WooExpert or Developer](https://woocommerce.com/customizations/) for assistance. We are unable to provide support for customizations under our  [Support Policy](http://www.woocommerce.com/support-policy/).
+
+This code allows you to unhook and remove the default WooCommerce emails.
+
+Add this code to your child theme’s `functions.php` file or via a plugin that allows custom functions to be added, such as the [Code snippets](https://wordpress.org/plugins/code-snippets/) plugin. Avoid adding custom code directly to your parent theme’s `functions.php` file, as this will be wiped entirely when you update the theme.
+
+```php
+if ( ! function_exists( 'YOUR_PREFIX_unhook_woocommerce_emails' ) ) {
+	/**
+	 * Callback for woocommerce_email action hook
+	 *
+	 * @param WC_Email $email_class An Email class instance.
+	 * @return void
+	 */
+	function YOUR_PREFIX_unhook_woocommerce_emails( $email_class ) {
+		/**
+		 * Hooks for sending emails during store events.
+		 */
+		remove_action( 'woocommerce_low_stock_notification', array( $email_class, 'low_stock' ) );
+		remove_action( 'woocommerce_no_stock_notification', array( $email_class, 'no_stock' ) );
+		remove_action( 'woocommerce_product_on_backorder_notification', array( $email_class, 'backorder' ) );
+
+		// New order emails.
+		remove_action( 'woocommerce_order_status_pending_to_processing_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
+		remove_action( 'woocommerce_order_status_pending_to_completed_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
+		remove_action( 'woocommerce_order_status_pending_to_on-hold_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
+		remove_action( 'woocommerce_order_status_failed_to_processing_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
+		remove_action( 'woocommerce_order_status_failed_to_completed_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
+		remove_action( 'woocommerce_order_status_failed_to_on-hold_notification', array( $email_class->emails['WC_Email_New_Order'], 'trigger' ) );
+
+		// Processing order emails.
+		remove_action( 'woocommerce_order_status_pending_to_processing_notification', array( $email_class->emails['WC_Email_Customer_Processing_Order'], 'trigger' ) );
+		remove_action( 'woocommerce_order_status_pending_to_on-hold_notification', array( $email_class->emails['WC_Email_Customer_On_Hold_Order'], 'trigger' ) );
+
+		// Completed order emails.
+		remove_action( 'woocommerce_order_status_completed_notification', array( $email_class->emails['WC_Email_Customer_Completed_Order'], 'trigger' ) );
+
+		// Note emails.
+		remove_action( 'woocommerce_new_customer_note_notification', array( $email_class->emails['WC_Email_Customer_Note'], 'trigger' ) );
+	}
+}
+add_action( 'woocommerce_email', 'YOUR_PREFIX_unhook_woocommerce_emails' );
+```