WooCommerce Print Invoices & Packing lists 3.13.7

* Fix - Sometimes printing multiple invoices would only render one page
* Fix - Prevent duplicate order ID titles from appearing when printing multiple invoices

* Fix - Missing placeholders in some Dutch translations

* Fix - Ensure plugin declares HPOS compatibility correctly
* Fix - Update SkyVerge Plugin Framework to 5.12.4, which addresses multiple JS errors

* Fix - Dutch translation generated a fatal error when enabled.
* Misc - Update the SkyVerge Plugin Framework to version 5.12.3

* Fix - German translation introduced an error when handling some placeholders in recent PHP versions

* Fix - Fix issue causing PHP warnings when Avatax is enabled

* Misc - Require PHP 7.4 and WordPress 5.6