WooCommerce One Page Checkout 2.8.5

* Tweak - WC 9.1 compatibility.

* Tweak - WP 6.6 compatibility.

* Tweak - WC 8.9 compatibility.
* Tweak - WP 6.5 compatibility.

Fix - Declare incompatibility with Cart/Checkout blocks.

* Fix - Prevent warnings if the post object becomes null during pageload.

Fix - Improved coding standards and escaping.

* Fix - Prevent ajax call if the add to cart ID cannot be found.
* Tweak - WC 7.3.0 compatibility.

* Fix - Escape and sanitizing bugfixes.

* Fix - Bug fixes.

* Fix - Fix: Ensure that the Storefront mini-cart can be expended and no console error is thrown when looking up an OPC product.