Create WorkloadGroup model (#111)

Author: ashleyvansp

KustoSchemaTools/Model/Cluster.cs

@@ -6,6 +6,7 @@ public class Cluster
         public string Url { get; set; }
         public List<DatabaseScript> Scripts { get; set; } = new List<DatabaseScript>();
         public ClusterCapacityPolicy? CapacityPolicy { get; set; }
+        public List<WorkloadGroup> WorkloadGroups { get; set; } = new List<WorkloadGroup>();
     }
 
 }