[Merged] Add Option for Additional Charges at Checkout

This request was merged into a consolidated ticket.

Please follow the active ticket here: https://feedback.manyrequests.com/p/add-ability-to-pass-stripe-processing-fees-to-clients-on

Original request:

Allow admins to add extra fees during checkout, such as transaction costs or credit card surcharges. This feature would make it possible to automatically include additional charges for specific payment methods, ensuring accurate billing and cost recovery.