IconicWP WooCommerce Delivery Slots 2.6.0

[fix] Fix license validation issues and type errors

[new] New Licensing system
[update] New filter `iconic_wds_fee_amount`
[update] Add timeslot argument to `iconic_wds_timeslot_shipping_method_allowed` filter
[fix] `FILTER_SANITIZE_STRING` is deprecated warnings in PHP 8.1
[fix] Admin: JS error when shipping method is not available for the given address

[fix] Fee not working when Auto-select First Timeslot setting is enabled