[#400] Fix GVL must support translations

[marco-prontera]

The goal of this PR is to enable the users of this repository to provide the language with variants (like pt-BR, pt-PT). This will enable us to fetch the correct translations of all capabilities (purpose, features, and so on), and to show to the user the most correct translation we can.

As we can see at this link https://register.consensu.org/Translation, the translations have a suffix that doesn't correspond to the language used in the TCModel since it uses the language with ISO-639-1 (it means it uses only two letters).

The solution I proposed is to use the most near language supported when the CMPs provide that language and update the list of supported languages since it's changed.
With these changes the GVL support the language and it's translations for every supported variant.
Of course for TCModel nothing is changed it will use only the first two letters of the language.
closes #400

[sevriugin]

@marco-prontera how this solution works if someone would like to load pt translation? It will return pt-PT ? The same for sr - it will be sr-Latin ? Could we add tests for these cases? Thanks 🙏

[marco-prontera]

@marco-prontera how this solution works if someone would like to load pt translation? It will return pt-PT ? The same for sr - it will be sr-Latin ? Could we add tests for these cases? Thanks 🙏

I introduced a test to cover all supported languages