Update csharp.md

Author: David

articles/cognitive-services/Speech-Service/includes/quickstarts/translate-stt/csharp/csharp.md

@@ -18,5 +18,7 @@ ms.author: erhopf
 [!INCLUDE [dotnet](./dotnet.md)]
 #### [.NET Core](#tab/dotnetcore)
 [!INCLUDE [dotnetcore](./dotnetcore.md)]
+#### [UWP](#tab/uwp)
+[!INCLUDE [uwp](./uwp.md)]
 
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