Add GetBlock API.md

GetBlock is also a Blockchain-as-a-service that offers API connection to multiple blockchains, please consider adding it to the list

README.md

@@ -270,6 +270,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Etherscan](https://etherscan.io/apis) | Ethereum explorer API | `apiKey` | Yes | Yes |
 | [Helium](https://docs.helium.com/api/blockchain/introduction/) | Helium is a global, distributed network of Hotspots that create public, long-range wireless coverage | No | Yes | Unknown |
 | [Nownodes](https://nownodes.io/) | Blockchain-as-a-service solution that provides high-quality connection via API | `apiKey` | Yes | Unknown |
+| [GetBlock](https://getblock.io/) | Blockchain RPC node provider that offers instant API access to over 50 multiple blockchains | `apiKey` | Yes | Unknown |
 | [Steem](https://developers.steem.io/) | Blockchain-based blogging and social media website | No | No | No |
 | [The Graph](https://thegraph.com) | Indexing protocol for querying networks like Ethereum with GraphQL | `apiKey` | Yes | Unknown |
 | [Walltime](https://walltime.info/api.html) | To retrieve Walltime's market info | No | Yes | Unknown |