Added Arca (Armenian Card) payment gateway (#631)

Author: k3rnel

README.md

@@ -107,6 +107,7 @@ Gateway | 2.x | 3.x | Composer Package | Maintainer
 [Alipay](https://github.com/lokielse/omnipay-alipay) | ✓ | ✓ | lokielse/omnipay-alipay | [Loki Else](https://github.com/lokielse)
 [99Bill](https://github.com/laraveler/omnipay-99bill) | - | ✓ | x-class/omnipay-99bill | [Laraveler](https://github.com/laraveler)
 [Allied Wallet](https://github.com/delatbabel/omnipay-alliedwallet) | ✓ | - | delatbabel/omnipay-alliedwallet | [Del](https://github.com/delatbabel)
+[Arca](https://github.com/k3rnel/omnipay-arca) | - | ✓ | k3rnel/omnipay-arca | [Poghos Boyajyan](https://github.com/k3rnel)
 [Authorize.Net](https://github.com/thephpleague/omnipay-authorizenet) | ✓ | ✓ | omnipay/authorizenet | [Jason Judge](https://github.com/judgej)
 [Authorize.Net API](https://github.com/academe/omnipay-authorizenetapi) | - | ✓ | academe/omnipay-authorizenetapi | [Jason Judge](https://github.com/judgej)
 [Authorize.Net Recurring Billing](https://github.com/cimpleo/omnipay-authorizenetrecurring) | - | ✓ | cimpleo/omnipay-authorizenetrecurring | [CimpleO](https://github.com/cimpleo)