YITH WooCommerce PDF Invoice 4.16.0

* New: Support for WooCommerce 4.7
* New: Support for WordPress 5.6
* Update: update plugin fw
* Dev: Auto select plugin enabled
* Dev: removed the .ready method from jQuery
* Dev: add a check to not include the VAT field if YITH EU VAT is installed

* New: Support for WooCommerce 4.6
* Update: plugin framework
* Dev: changes in the get order date method

* New: Support for WooCommerce 4.5
* New: Integration with YITH Frontend Manager for WooCommerce
* Update: plugin framework
* Update: language files
* Fix: fixed fatal error
* Fix: avoid displaying credit note documents in orders in My Account page if option is not enabled
* Dev: changes in the credit note with products
* Dev: added new filter yith_ywpi_validate_checkout_fields_conditions
* Dev: improved the credit note
* Dev: remove the precision in the credit note % tax
* Dev: convert state code and convert it to the state name
* Dev: optional label on checkout can be now translated
* Dev: added new filter ywpi_checkout_optional_label