Add the release notes to PackageReleaseNotes

Author: wallymathieu

Directory.Build.props

@@ -30,6 +30,8 @@
     <!-- disable sourcelink on mono, to workaround https://github.com/dotnet/sourcelink/issues/155 -->
     <EnableSourceLink Condition=" '$(OS)' != 'Windows_NT' AND '$(MSBuildRuntimeType)' != 'Core' ">false</EnableSourceLink>
     <EnableSourceControlManagerQueries>$(EnableSourceLink)</EnableSourceControlManagerQueries>
+    <PackageReleaseNotes>$([System.IO.File]::ReadAllText("$(MSBuildThisFileDirectory)/RELEASE_NOTES.txt"))</PackageReleaseNotes>
+
   </PropertyGroup>
 
   <!-- mono -->