Overhaul French translation

The current French translation of Pleroma-FE is basically a joke. It looks like most of it has been Google-translated, with a lot of weird phrasings, and also it's really incomplete.
This MR completes the translation and fixes most of the weird things. It also replaces gender-inclusive language to simple masculine (the point médian is hostile to readability and screenreaders), as well as replacing some anglicisms with actual French words.
There's still some rough edges remaining, but overall I think it's ready.