YITH Advanced Refund System for WooCommerce Premium 1.34.0

* New: Support for WooCommerce 4.0
* New: Support for WordPress 5.4
* New: Elementor widget - Refund Requests
* New: Elementor widget - View Request
* Update: Plugin framework
* Update: Language files
* Fix: Sequential order number compatibility
* Dev: Added filter "yith_wcars_order_date"
* Dev: Added filter "yith_ywcars_my_refund_requests_endpoint"

* New: Support for WooCommerce 3.9
* New: Added {items_table} placeholder for admin email (new refund request received)
* New: Compatibility with YITH WooCommerce Sequential Order Number
* Update: Plugin framework
* Update: Language files
* Fix: Improved refund process

* Update: Plugin framework