Added Microsoft.NETFramework.ReferenceAssemblies

MicroStationTagExplorer.sln

@@ -36,6 +36,7 @@ EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "props", "props", "{4040A339-594D-435E-BEEB-2E5E435BD5E9}"
 	ProjectSection(SolutionItems) = preProject
 		build\Base.props = build\Base.props
+		build\ReferenceAssemblies.props = build\ReferenceAssemblies.props
 		build\XUnit.props = build\XUnit.props
 	EndProjectSection
 EndProject

build/ReferenceAssemblies.props

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0-preview.1" />
+  </ItemGroup>
+</Project>