Make ISO3166 more "extendable"

[alexandrmazur96]

Unfortunately, because ISO3166 have private visibility modifier on its internal "dataset" ($countries) –

https://github.com/thephpleague/iso3166/blob/74a08ffe08d4e0dd8ab0aac8c34ea5a641d57669/src/ISO3166.php#L160

we can do nothing to provide more library custom functionality in the project.

For example, we need to consider the CI (Canary Islands) country code as Spain, so one of the possible solutions for that is to include CI in the dataset, but I can't extend it without copy-paste the whole ISO3166 class.

Raising the visibility level to protected will allow me to extend your class and modify the dataset for my needs. Moreover, it does not even look like BC.

[alcohol]

You can decorate the class.