Investigate support for C++20 standard

[vvish]

For demonstration purposes the library was intentionally designed to use relevant C++23 features.

In fact, considering level of support by compilers, only the following standard facilities were used:

• error reporting by default is done using std::expected;
• std::to_underlying is used.

Regarding std::expected: configurable error reporting (#9) can be leveraged to support client-specified error reporting facilities.
Utility std::to_underlying has trivial implementation.

Research is needed to define scope and breakdown of the issue