Add doc for installing Windows Service in .NET Core context

Looking for "install Windows Service" I go to this topic

https://docs.microsoft.com/en-us/dotnet/framework/windows-services/how-to-install-and-uninstall-services

It should work for .NET Core services (at least `new-service` should definitely work, as it just pinvokes to CreateServiceW etc, not sure what InstallerUtil assumes) and since we know Windows Services are heavily used as a vehicle for .NET Core worker services we should probably have a topic that is not .NET Framework aligned. It most likely can simply point everyone at the `new-service` cmdlet.

@bradygaster @DamianEdwards anything to add?