List Opayo alongside Sage Pay

The Sage Pay gateway is being renamed to Opayo. The driver remains unchanged, but the mention is needed for users looking for an Opayo driver.

README.md

@@ -255,7 +255,7 @@ Gateway | 2.x | 3.x | Composer Package | Maintainer
 [RentMoola](https://github.com/rentmoola/omnipay-rentmoola) | ✓ | - | rentmoola/omnipay-rentmoola | [Geoff Shaw](https://github.com/Shawg)
 [RoboKassa](https://github.com/hiqdev/omnipay-robokassa) | ✓ | ✓ | hiqdev/omnipay-robokassa | [HiQDev](https://github.com/hiqdev)
 [RocketGate](https://github.com/mvestil/omnipay-rocketgate) | ✓ | ✓ | mvestil/omnipay-rocketgate | [Mark Vestil](https://github.com/mvestil)
-[Sage Pay](https://github.com/thephpleague/omnipay-sagepay) | ✓ | ✓ | omnipay/sagepay | [Jason Judge](https://github.com/judgej)
+[Sage Pay (now Opayo)](https://github.com/thephpleague/omnipay-sagepay) | ✓ | ✓ | omnipay/sagepay | [Jason Judge](https://github.com/judgej)
 [Sberbank](https://github.com/AndrewNovikof/omnipay-sberbank) | - | ✓ | andrewnovikof/omnipay-sberbank | [Andrew Novikov](https://github.com/AndrewNovikof)
 [SecPay](https://github.com/justinbusschau/omnipay-secpay) | ✓ | - | justinbusschau/omnipay-secpay | [Justin Busschau](https://github.com/justinbusschau)
 [SecurePay](https://github.com/thephpleague/omnipay-securepay) | ✓ | ✓ | omnipay/securepay | [Omnipay](https://github.com/thephpleague/omnipay)