WooCommerce Product Add-Ons 6.8.2

* Fix - Honor taxes in Customer Defined Price add-ons when store shows prices including tax.

* Fix - Prevent negative input on price addons when min restrictions are enabled.
* Fix - Removed support for versions of WC 3.0 and below.
* Fix - Reordering Product Add-Ons with email address should not remove @ characters.
* Fix - Use h2 instead of h3 element for addon headings.
* Fix - Wrap addons in a `wc-pao-addons-container` div.
* Tweak - WC 5.1 compatibility.
* Tweak - WP 5.7 compatibility.

* Fix - Add Better guards for WC Navigation not being enabled.