message: add custom types sub package
diff: @@ -131,6 +131,8 @@ java: true
  sync-methods: none
  add-context-parameter: true
  generate-client-interfaces: false
  +custom-types-subpackage: implementation.models
  +custom-types: AnalyzeResult
  license-header: |-
  Copyright (c) Microsoft Corporation. All rights reserved.
  Licensed under the MIT License.
  