Parse refresh token from create token response

Author: KoditkarVedant

Src/Notion.Client/Api/Authentication/CreateToken/Response/CreateTokenResponse.cs

@@ -7,6 +7,9 @@ public class CreateTokenResponse
         [JsonProperty("access_token")]
         public string AccessToken { get; set; }
 
+        [JsonProperty("refresh_token")]
+        public string RefreshToken { get; set; }
+
         [JsonProperty("token_type")]
         public string TokenType { get; set; } = "bearer";