French (FR) localization

[kravhen]

Related to #7

Description

I've implemented french localization (and hardcoded string extraction) locally. Always wanted to learn the localization workflow on android and seemed a good idea to give it a try with an app that's still young and hasn't grown too complex yet.

I can turn this into a draft PR for now if it's better and keep an eye on how things evolve and demand for translations grow.

I see a bunch of other localization/translation issues and PRs so far.
Maybe there could also can be a tracking/umbrella issue to consolidate different folks' efforts, keep track of progress of different PRs, agree on conventions, avoid duplicate work (e.g. hardcoded string extraction)?

Checklist

• I have read the contribution guidelines: https://github.com/permissionlesstech/bitchat-android?tab=readme-ov-file#contributing
• I have performed a self-review of my code

• I have mentioned the corresponding issue and the relevant keyword (e.g., "Closes: #xy") in the description (see https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue)
• [n/a] If it is a core feature, I have added automated tests

[MutantRabbit767]

this is awesome