Add test for consuming .NET Standard 2.0 library from .NET Framework 4.6.1 project

TestAssets/DesktopTestProjects/NETFrameworkReferenceNETStandard20/TestApp/Program.cs

@@ -0,0 +1,15 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+
+namespace TestApp
+{
+    class Program
+    {
+        public static void Main(string[] args)
+         {
+             Console.WriteLine(TestLibrary.Helper.GetMessage());
+         }
+    }
+}

TestAssets/DesktopTestProjects/NETFrameworkReferenceNETStandard20/TestApp/TestApp.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net461</TargetFramework>
+  </PropertyGroup>
+
+    <ItemGroup>
+    <ProjectReference Include="..\TestLibrary\TestLibrary.csproj" />
+  </ItemGroup>
+
+</Project>