Change the i18n system

[benoit74]

Currently, for i18n we rely directly on system locale. We should depend on and use an external locale-data such as what Babel does.

This would provide a real support for Alpine Linux for instance (see https://github.com/openzim/python-scraperlib/pull/133#pullrequestreview-1877241783 for more context / details about Alpine issue) and less system-dependent behaviors.

We have to check all our use cases to check how to implement this with minimal/no impact.