Incomplete ISO639_3 Language List

[MrSampson]

Hi,
The pydantic-extra-types library validates ISO 639-3 codes using pycountry.languages (see pydantic_extra_types/language_code.py:239). However, pycountry 24.6.1 has incomplete ISO 639-3 coverage and is missing many valid codes including:

- eml (Emiliano-Romagnolo)
- others?

Looking at pycountry, it seems like the developer is not really into keeping the list accurate:

No changes to the data will be accepted into pycountry. This is a pure wrapper around the ISO standard using the pkg-isocodes database from Debian as is. If you need changes to the political situation in the world, please talk to the ISO or Debian people, not me.

Maybe pydantic-extra-types should use iso639-lang instead?