Add letterboxparcel 48 hours

[OlfatProgressus]

All Submissions:

• Does your code follow WooCommerce and WordPress standards?
• Have you successfully run tests with your changes locally?
• Have you tested both blocks/non-blocks cart/checkout?
• Have you tested the cart and checkout as both a logged-in user and a guest?
• Have you successfully placed an order as both a logged-in user and a guest?
• Did you have the query monitor plugin active during all testing?

Changes proposed in this Pull Request:

Closes # .
Task url

How to test the changes in this Pull Request:

1. Check PostNL settings you should find a new dropdown for "Default automatic letterboxparcel product" and a new input for Extra fee for the letterboxparcel (24 hours)
2. Add a new product that eligible for letterbox to the cart then go to checkout page, you will find the shipping option is shown based on the admin selection.
3. Create a new order then generate the label, check logs you will find the product code 2928 if it is letterbox 24 and 2948 if it is letterbox 48

Other information:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changelog entry

Enter a summary of all changes on this Pull Request. This will appear in the changelog if accepted.