Add SqlQuerySpec to migration guide.

Author: j82w

articles/cosmos-db/sql/migrate-dotnet-v3.md

@@ -128,6 +128,12 @@ The following properties have been removed:
 
 * `FeedOptions.PopulateQueryMetrics`
 
+### Changes to SqlQuerySpec (QueryDefinition in v3.0 SDK)
+
+The `SqlQuerySpec` class in SDK v2 has now been renamed to `QueryDefinition` in the SDK v3, and can be viewed in the [sample](#query-items) below.
+
+`SqlParameterCollection` and `SqlParameter` has been removed. Parameters are now added to the `QueryDefinition` with a builder model using `QueryDefinition.WithParameter`. Users can access the parameters with `QueryDefinition.GetQueryParameters`
+
 ### Constructing a client
 
 The .NET SDK v3 provides a fluent `CosmosClientBuilder` class that replaces the need for the SDK v2 URI Factory.