WooCommerce Chained Products 3.7.0

* New: WooCommerce 4.8.1, 4.9.3, 5.0.1, 5.1.1, 5.2.3, 5.3.1, 5.4.2, 5.5.1 compatible
* New: WordPress 5.8.0 compatible
* New: Function 'get_chained_parent_ids' to find parent products ids in which a product is linked as chained product
* Fix: PHP Fatal error: Uncaught WC_Data_Exception: Invalid tax class
* Fix: Yith WooCommerce Added to Cart Popup Premium not working on a chained product
* Update: Set stock status of chained parent based on stock status of its chained child
* Update: POT file

* New: WooCommerce 4.6.2, 4.7.1 compatible
* Developer: Filter 'chained_products_show_for_variable'
* Update: POT file

* New: WooCommerce 4.5.2 compatible
* Fix: Fatal error when updating existing orders with Chained Products
* Fix: Fatal error when editing variable products in admin
* Update: Check order instance before calling order functions