* Fix - Fix styling bugs and theme conflicts in the email customizer caused by theme stylesheets and incorrect CSS selectors.
* Tweak - WC 5.1 compatibility.
* Tweak - WP 5.7 compatibility.
* Fix - add product page & docs links for convenience.
* Tweak - WC 5.0 compatibility.
* Tweak - WP 5.6 compatibility.