* Feature - The admin interface has been completely rebuilt with a new add-on list screen and single add-on screens!
* Feature - Add 'description' field for add-ons
* Feature - Add the ability to enable/disable add-ons
* Tweak - Move checkout add-on location settings to the customizer in WC 3.3+
* Fix - Fix required checkbox validation for older WooCommerce versions
* Fix - Fix issue with apostrophes not being unescaped on newer versions of WooCommerce
* Misc - Remove support for WooCommerce 2.6
* Dev - Add filter `wc_checkout_add_ons_meta_box_add_on_fields` which filters the fields available in the new Add-On Data meta box
* Dev - Add filter `wc_checkout_add_ons_meta_box_add_on_panels` which filters the panels shown on the new Add-On Data meta box
* Dev - Add filter `wc_checkout_add_ons_get_field_renderer`, allowing the rendering function for a given field to be overridden
* Dev - Add filter `wc_checkout_add_ons_add_on_list` which filters the add-ons available in the add-on list
