* add - adds `user_data` event on checkout page after filling email/phone fields
* add - adds `user_data` event on all pages if user is logged in
* tweak - tested against the latest version of WordPress
* add - adds fallback for `add_payment_info` and `add_shipping_info` in case of non-standard checkout layouts
* add - adds `user_data` property to `purchase` event
* add - unifies `user_data` event format
* tweak - tested against the latest version of WooCommerce
* add - add `content_type` property to event's items
* tweak - tested against the latest versions of WordPress and WooCommerce
* add - add 'customer_type' property to the 'purchase' event to distinguish between new and returning customers
* add - add 'payment_type' property to the 'purchase' event
* fix - fix issue with 'add_to_cart' event on product page, related to product variants
* fix - fix issue with 'add_to_cart' event on cart page, related to product variants
* tweak - tested against the latest version of WooCommerce
* add - improve conversion tracking monitoring UI and documentation
* tweak - tested against the WooCommerce 10!
* fix - `value` property in `add_to_cart` event
* tweak - tested against the latest version of WooCommerce