YITH WooCommerce Pre-Order Premium 2.23.2

* New: Support for WooCommerce 4.2
* New: Option "Prevent adding more than one Pre-Order product to the cart"
* Fix: Elementor widget for Availability Date

* New: Support for WooCommerce 4.0
* New: Support for WordPress 5.4
* New: Elementor widget - Availability Date
* New: Elementor widget - Show Pre-Order Products
* Update: Plugin framework
* Update: Language files

* New: Support for WooCommerce 3.9
* Update: Plugin Core
* Update: Language files