Input validation does not work

[ArtyomVancyan]

There is no way to check the input validation.

PR:

• Implement a way to check the validation #25

[ArtyomVancyan]

It has been decided to have an onValidate property in release v0.1.0 which was supposed to be a callback to take control of the validation. But then I thought it would be more efficient if we had a boolean property in the value object that would contain the real-time validity of the input value depending on the selected country.