YITH WooCommerce EU VAT Premium 2.31.0

* New: Support for WooCommerce 4.0
* New: Support for WordPress 5.4
* New: Added new option to let the admin choose the behavior of the VAT field if the VIES server is not responding
* Tweak: Add a red/green border to the VAT field depending on the response
* Tweak: Added validation classes to the VAT field
* Update: Plugin framework
* Update: Language .pot file
* Dev: Added an exception to check when the VIES server is not responding
* Dev: All strings escaped

* New: support for WooCommerce 3.9
* Tweak: show eu vat amount on checkout before other rows
* Update: plugin framework
* Update: Spanish language
* Fix: fixed VAT Number value in billing fields in the order details from admin side
* Fix: remove eu vat from shipping
* Fix: added a condition to not show the price for free shipping
* Fix: fixed the amount exempted when there is more than one product in cart
* Fix: obtain the correct country when specifying a country in WooCommerce general settings
* Fix: avoid getting the VAT number from my account when the VAT input is hidden in the checkout
* Dev: new filter 'yith_ywev_add_label_shipping_tax'
* Dev: added the placeholder in VAT field of my account page
* Dev: Minified JS file

* New: support for WordPress 5.3
* New: support for WooCommerce 3.8
* Update: plugin framework
* Update: Italian language
* Update: Dutch language
* Update: updated the wpml-config.xml file
* Fix: fixed a problem with the thousand values
* Fix: vat number field now is hidden when checkout page is loaded with the option 'Disable VAT exception in same country' selected
* Dev: new filter yith_eu_vat_field_priority