Register the Yaml reader with our factory's registry for parsing of YAML docs

Author: MaggieKimani1

src/Microsoft.OpenApi.Workbench/MainModel.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using System;
@@ -203,6 +203,9 @@ protected void OnPropertyChanged(string propertyName)
         /// </summary>
         internal async Task ParseDocumentAsync()
         {
+            OpenApiReaderRegistry.RegisterReader(OpenApiConstants.Yaml, new OpenApiYamlReader());
+            OpenApiReaderRegistry.RegisterReader(OpenApiConstants.Yml, new OpenApiYamlReader());
+
             Stream stream = null;
             try
             {