Proposal: Move Entity and ValueObject to a separate nuget

[AlexanderDorofeev]

Vladimir, it looks like Entity and ValueObject are not a part of language extensions. They are a part of the domain layer building block. And there is a conflict in responsibilities. Not all domain models rely on functional programming style, also we don't need domain classes in all projects, that use functional programming style. So it looks reasonable to extract these classes into separate domain building block\nuget and it would be nice to have your specification pattern there, cos it is part of a domain. What do you think about that?

[vkhorikov]

Yes, I plan to do this ( https://github.com/vkhorikov/CSharpFunctionalExtensions/issues/323#issuecomment-916041498 ), but not sure when I'd be able to implement such a split, the project will need to be carefully split in pieces while preserving backward compatibility.