Add in cswinrt KnownFrameworkReference

TestAssets/TestProjects/UseCswinrt/Program.cs

@@ -0,0 +1,14 @@
+using System;
+using Windows.Data.Json;
+
+namespace consolecswinrt
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var rootObject = JsonObject.Parse("{\"greet\": \"Hello\"}");
+            Console.WriteLine(rootObject["greet"]);
+        }
+    }
+}

TestAssets/TestProjects/UseCswinrt/consolecswinrt.csproj

@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<OutputType>Exe</OutputType>
+		<TargetFramework>net5.0</TargetFramework>
+		<TargetPlatformIdentifier>Windows</TargetPlatformIdentifier>
+	</PropertyGroup>
+</Project>