V4 CI Build no longer works

[CharliePoole]

This is primarily due to our switching from AppVeyor to GitHub Actions, which is not reflected in the v4 code. In addition, runtimes past EOL, which were removed in version 3, must also be removed from the version 4 codebase.

The aim of this issue is to simply get the CI working again, without adding any improvements.

[CharliePoole]

This issue has been resolved in version 4.0.0-beta.1

The release is available on:
GitHub.
NuGet packages are also available NuGet.org and
Chocolatey Packages may be found at Chocolatey.org