[Enhancement] Add support for nullable reference types

[thomasgalliker]

Summary

Extend the library to support C# nullable reference types (string?, MyClass?, etc.), ensuring that object inspection correctly represents null values and distinguishes between nullable and non-nullable types in its output. This enhancement would improve debugging and logging scenarios in projects that rely on modern C# language features.

API Changes

Public APIs should explicitly support nullable reference types, for example allowing parameters to be declared as object? where appropriate.

Intended Use Case

Developers using C# 8.0+ with nullable reference types need accurate representation of null values when inspecting objects, preventing ambiguity and improving clarity in diagnostic output.