Correct documentation generation for nanoFramework.TestFramework (#262)

***NO_CI***

Author: frobijn

source/TestFramework/nanoFramework.TestFramework.nfproj

@@ -19,6 +19,7 @@
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
     <RestoreLockedMode Condition="'$(TF_BUILD)' == 'True' or '$(ContinuousIntegrationBuild)' == 'True'">true</RestoreLockedMode>
     <LangVersion>default</LangVersion>
+    <DocumentationFile>bin\$(Configuration)\nanoFramework.TestFramework.xml</DocumentationFile>
   </PropertyGroup>
   <PropertyGroup>
     <SignAssembly>true</SignAssembly>