Want to embed a changelog file's content inside the <PackageReleaseNotes> in your libraries, so it is readily visible on NuGET, you can do the following:

embed-changelog-in-library.csproj

<!-- 
Automatically copy the content of a CHANGELOG.md file into a NuGET package's change log section via the `<PackageReleaseNotes>` element in .csproj by doing the following:

Put the following into your .csproj, e.g. `Lib.csproj`, and the content of your CHANGELOG.md will be embedded when the project is packaged.

This assumes that the project structure is as follows:

\CHANGELOG.md
\src\Lib\Lib.csproj
-->
<Target Name="SetPackageReleaseNotes" BeforeTargets="GenerateNuspec">
  <PropertyGroup>
    <PackageReleaseNotes>$([System.IO.File]::ReadAllText("$(MSBuildProjectDirectory)/../../CHANGELOG.md"))</PackageReleaseNotes>
  </PropertyGroup>
</Target>