feat: Update getPaymentData method to accept a reference parameter

[Freddy10035]

This is to handle

GuzzleHttp\Exception\ClientException Client error: GET https://api.paystack.co/transaction/verify/ resulted in a 400 Bad Request response: { "status": false, "message": "Transaction ID should be numeric." }

error that people keep on getting when using this with laravel.

[Freddy10035]

DO NOT MERGE

[chrisidakwo]

DO NOT MERGE

Is there any reason why this should not be merged?

@unicodeveloper I just came across this issue when trying to verify a payment from a payment page. On successful transaction, the Paystack payment page sends reference as the query param rather than trxref. Hence, either the verifyTransactionAtGateway() method is updated to account for a reference query param or devs are given the option in getPaymentData() to provide the reference however they receive from Paystack - I prefer this option.

@Freddy10035 Pls see my comment on your changes