WooCommerce PDF Product Vouchers 3.12.3

* Tweak - Use a related order's currency rather than the store default currency for vouchers, whenever possible
* Fix - When a voucher has a limit on characters set in the optional message to recipient, count Unicode (e.g. accented) characters correctly
* Fix - When the My Account page is set as the home page make sure that the Vouchers page is accessible
* Fix - Allow adding notes to a voucher that is being created manually in admin before it is saved for the first time or the PDF has been generated
* Fix - Save notes added when redeeming vouchers via the modal popup in the Vouchers admin edit screen
* Fix - Harden some method calls when getting the currency from an order, in case it's not an order object of the expected type
* Fix - Replace the textdomain of some gettext strings with the correct one for this plugin
* Fix - Pass a default value of null in `woocommerce_loop_add_to_cart_link` filter callback so that no errors would be triggered in some instances when no value is passed

* Fix - Correctly apply tax to vouchers when product prices are configured to be tax inclusive

* Fix - Ensure correct discount calculation when multi-purpose vouchers are redeemed on orders containing subscriptions
* Fix - Correctly apply partially-redeemed vouchers to shopping carts
* Fix - Do not use purchaser name in place of the recipient name if the recipient name is empty
* Fix - When a voucher is on sale, calculate the tax from the regular voucher price so it is correct when redeemed
* Tweak - Limit the product "redeemable by" select field to vouchers that can be redeemed online
* Dev - Fix typo in filter: `wc_pdf_prdouct_vouchers_voucher_search_fields` is now `wc_pdf_product_vouchers_voucher_search_fields`
* Dev - Add missing $email argument to `woocommerce_email_header` and `woocommerce_email_footer`