Wrong "gateway" name for Google Pay integration

[apetrosyan93]

I tried your wallet.js and after some testing and getting wrong api responses from fluidpay, i tried to see how it works in the code.
I noticed that "gateway" param changed for fluidpay, and now it has different value from that in wallet.js
https://github.com/fluidpay/walletjs/blob/master/src/googlepay.js

I am pretty sure you know about, but when testing i lost some time. Maybe you will correct it soon.
https://developers.google.com/pay/api/web/guides/tutorial