Resource not accessible by integration

- Add lib or ref assemblies for the netstandard2.0 target framework

Some target frameworks declared in the dependencies group of the nuspec and the lib/ref folder do not have exact matches in the other location. Consult the list of actions below:

Cannot convert null literal to non-nullable reference type.

Non-nullable property 'Value' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'Nested' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Nullability of type of parameter 'obj' doesn't match overridden member (possibly because of nullability attributes).

Cannot convert null literal to non-nullable reference type.

Non-nullable property 'Value' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'Nested' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.