Automatically publish tags to NuGet with Trusted Publishing

[mus65]

this automates the publishing of releases to nuget.org and makes use of trusted publishing. See

https://learn.microsoft.com/en-us/nuget/nuget-org/trusted-publishing
https://devblogs.microsoft.com/dotnet/enhanced-security-is-here-with-the-new-trust-publishing-on-nuget-org/

This is obviously untested and would require setup in GitHub and NuGet:

• a NUGET_USER secret must be added to the Repository settings
• Trusted publishing must be set up on nuget.org as described here

[Rob-Hague]

Let's try it