WooCommerce Royal Mail / Royal Mail Shipping Method for WooCommerce 3.6.4

* Tweak - WooCommerce 10.6 Compatibility.

* Fix - International Tracked & Signed now supports MEDIUM_PARCEL up to 20kg for custom boxes.
* Tweak - WooCommerce 10.5 Compatibility.

* Tweak - WordPress 6.9 and WooCommerce 10.4 Compatibility.

* Tweak - WooCommerce 10.3 Compatibility.

* Add - October 2025 regular and online pricing changes.

* Update - Parcelforce & International Tracked rates.
* Tweak - WooCommerce 10.2 Compatibility.

* Tweak - WooCommerce 10.1 Compatibility.

* Tweak - WooCommerce 10.0 Compatibility.

Tweak - WooCommerce 9.9 Compatibility.

* Update Requires headers for WooCommerce compatibility.
* Update to ubuntu-latest to fix QIT tests.