PayPal anti-fraud check for subscriptions

[rvdsteege]

While checking the Mollie docs for support ticket https://secure.helpscout.net/conversation/2626471877/27357, I noticed that PayPal requires an anti-fraud check script (FraudNet) to be loaded on the checkout page. I'm not sure if this is new? We might need to add support for this in this library.

https://docs.mollie.com/docs/recurring-payments#charging-recurring-payments-via-paypal