Added information on the Gemini API (#797)

README.md

@@ -181,6 +181,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Coinpaprika](https://api.coinpaprika.com) | Cryptocurrencies prices, volume and more | No | Yes | Yes |
 | [CryptoCompare](https://www.cryptocompare.com/api#) | Cryptocurrencies Comparison | No | Yes | Unknown |
 | [Cryptonator](https://www.cryptonator.com/api/) | Cryptocurrencies Exchange Rates | No | Yes | Unknown |
+| [Gemini](https://docs.gemini.com/rest-api/) | Cryptocurrencies Exchange | No | Yes | Unknown |
 | [Livecoin](https://www.livecoin.net/api) | Cryptocurrency Exchange | No | Yes | Unknown |
 | [MercadoBitcoin](https://www.mercadobitcoin.net/api-doc/) | Brazilian Cryptocurrency Information | No | Yes | Unknown |
 | [Nexchange](https://nexchange2.docs.apiary.io/) | Automated cryptocurrency exchange service | No | No | Yes |