refs and cleanup

Author: SimonCropp

src/Directory.Packages.props

@@ -8,7 +8,7 @@
     <PackageVersion Include="Caseless.Fody" Version="1.9.1" />
     <PackageVersion Include="EmptyFiles" Version="8.9.1" />
     <PackageVersion Include="Fody" Version="6.9.2" />
-    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="27.0.2" />
+    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.1" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
     <PackageVersion Include="Polyfill" Version="7.30.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.150" />