YITH WooCommerce Wishlist Premium 3.31.0

* Fix: moved check over Ajax Loading option on first wishlist init only, to avoid problems when dynamically loading ATW on variable products

* New: support for WooCommerce 4.2
* Update: plugin framework
* Tweak: set minimum item quantity to 1
* Tweak: added WordPress among blocked bot user agents
* Tweak: make sure to finalize session when possible
* Tweak: added link to product in wishlist mobile template
* Fix: Prevent error if default wishlist doesn't exists
* Fix: update button not saving items position
* Fix: correctly applied yith_wcwl_is_wishlist_responsive filter to yith_wcwl_is_mobile function
* Fix: wrong check over show_ask_an_estimate_button
* Fix: avoid to use cache that cannot be invalidated (stop caching queries results, use cache for user wishlists)
* Fix: Ask an Estimate button on mobile footer not using dedicated label option
* Fix: additional info popup not appearing for guest users
* Fix: clear_caches method wasnt properly cleaning cache for guest users
* Dev: added yith_wcwl_ask_for_an_estimate_popup_text filter
* Dev: added yith_wcwl_show_wishlist_update_button filter
* Dev: added yith_wcwl_add_to_wishlist_icon_html filter
* Dev: added yith_wcwl_add_to_wishlist_heading_icon_html filter
* Dev: added yith_wcwl_add_to_wishlist_data trigger, to allow third party code change data submitted with ATW ajax call

* New: support for WooCommerce 4.1
* New: prevent some UserAgents from triggering wishlist handling (avoid spam)
* New: added minor css fixes for Storefront theme
* New: added option to choose whether to automatically close feedback popup or not
* Update: plugin framework
* Tweak: added product_url placeholder for promotional email body
* Tweak: review add process, to avoid unnecessary items update
* Tweak: items are now counted per ID instead of user_id
* Tweak: show variation attributes on Popular table
* Tweak: changed 'Price' by 'Unit price' on wishlist modern view
* Tweak: improved localized date on wishlist table
* Tweak: added wishlist as gutenberg block in new wishlist page
* Tweak: added "Wishlist page" post status
* Tweak: added new check to avoid "Cannot read property contains of undefined" error
* Tweak: added search box to All Wishlist view
* Tweak: added default values for email contents on plugin options
* Tweak: user can now delete also default wishlist
* Tweak: minor changes to 'manage modern' layout
* Tweak: added view > and close links to confirmation popup
* Fix: solved issue with item counts, when filtering per product
* Fix: fixed billing last name value on 'promotional', 'on sale' and 'back in stock' emails
* Fix: show remove button on list mobile when at least one of the two buttons is shown on desktop
* Fix: notice due to undefined widgets attributes
* Fix: fatal error on empty wishlist page
* Fix: added some checks to avoid fatal errors in back in stock email
* Dev: added yith_wcwl_create_wishlist_button_label filter
* Dev: added yith_wcwl_wishlist_download_url filter
* Dev: added yith_wcwl_is_wishlist_responsive filter, to allow developers disable responsive behaviour for the wishlist
* Dev: added yith_wcwl_generated_default_wishlist action
* Dev: added yith_wcwl_default_wishlist filter
* Dev: added yith_wcwl_add_notice wrapper function, to avoid possible fatal errors when calling wc_add_notice