add BitcoinPayBox to the list of HOS

Closes #1446

Author: pavlenex

docs/Deployment/HardwareAsAService.md

@@ -22,6 +22,7 @@ Here you can find a non-exhaustive list of companies that provide such a service
 - [Umbrel](https://umbrel.com/)
 - [Embassy](https://start9.com/)
 - [Citadel](https://runcitadel.space/)
+- [BitcoinpayBox](https://bitcoinpaybox.es/)
 
 Do you provide Hardware As A Service and are not listed here?
 Open an issue to [get added to this list](https://github.com/btcpayserver/btcpayserver-doc/issues)