Use JObject so GraphQLQuery can be deserializable passing object as variables. (graphql-dotnet#530)

Since GraphQL tool pass query parameter as an object, somehow this makes deserialization of query parameter failed as null.  Changing it JObject to guarantee success.

Author: ruxo

src/GraphQL.GraphiQL/Controllers/GraphQLController.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Net;
 using System.Net.Http;
 using System.Text;
@@ -38,7 +38,7 @@ public GraphQLController(
         [HttpGet]
         public Task<HttpResponseMessage> GetAsync(HttpRequestMessage request)
         {
-            return PostAsync(request, new GraphQLQuery { Query = "query foo { hero }", Variables = "" });
+            return PostAsync(request, new GraphQLQuery { Query = "query foo { hero }", Variables = null });
         }
 
         [HttpPost]
@@ -82,6 +82,6 @@ public class GraphQLQuery
         public string OperationName { get; set; }
         public string NamedQuery { get; set; }
         public string Query { get; set; }
-        public string Variables { get; set; }
+        public Newtonsoft.Json.Linq.JObject Variables { get; set; }
     }
 }