Clarify WPF specific concerns with MSBuild

A couple of errors can arise when using GitVersion.MSBuild with
different versions of the .NET Core SDK. This will help users know what
to do based off what version they are using (not necessarily what they
are targeting).

Author: hymccord

docs/input/docs/usage/msbuild.md

@@ -51,16 +51,39 @@ The next thing you need to do is to remove the `Assembly*Version` attributes fro
 your `Properties\AssemblyInfo.cs` files. This puts GitVersion.MsBuild in charge of
 versioning your assemblies.
 
-DotNet SDK-style projects will generate Assembly Version info along with other
-Assembly Info in a 'projectname.AssemblyInfo.cs' file, conflicting with GitVersion.
-So, you will need to edit your project. Add [GenerateAssemblyFileVersionAttribute](https://docs.microsoft.com/en-us/dotnet/core/project-sdk/msbuild-props#generateassemblyfileversionattribute)
-under the first PropertyGroup and set it to `false`:
+### WPF specific concerns
+
+One futhur step needs to be taken for SDK-style WPF projects.
+
+Building projects with .NET Core SDK with a version lower than v5.0.200
+requires turning off automatic generation of the different versioning attributes.
+GitVersion usually controls these properties but cannot during WPF specific
+targets that generate a temporary project.
 
 ```xml
-<!-- GitVersion DotNet SDK Compatibility -->
-<GenerateAssemblyFileVersionAttribute>false</GenerateAssemblyFileVersionAttribute>
+<PropertyGroup>
+  <!-- Wpf workaround: GitVersion and .NET SDK < v5.0.200 -->
+  <GenerateAssemblyFileVersionAttribute>false</GenerateAssemblyFileVersionAttribute>
+  <GenerateAssemblyInformationalVersionAttribute>false</GenerateAssemblyInformationalVersionAttribute>
+  <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
+</PropertyGroup>
 ```
 
+For .NET Core SDK v5.0.200 to v6.0.0-preview.1, a opt-in flag was introduced to
+allow package references to be imported to the temporary project.
+You can now remove the previous versioning attributes and replace them with
+a single property.
+
+```xml
+<PropertyGroup>
+  <!-- WPF workaround: GitVersion and .NET SDK between v5.0.200 and v6.0.0-preview.2  -->
+  <IncludePackageReferencesDuringMarkupCompilation>true</IncludePackageReferencesDuringMarkupCompilation>
+</PropertyGroup>
+```
+
+You can remove all workarounds if you are building with .NET Core SDK
+v6.0.0-preview.2 or later as the flag is now opt-out.
+
 ### Done!
 
 The setup process is now complete and GitVersion.MsBuild should be working its magic,