French translation update

[Franck-Berry]

Hello,

I am the (French) person who for 2 years has been translating Material Skin into French (Franck-Berry on github.com, Franck@ on forums.slimdevices.com). During these two years, I gained a little more confidence in my abilities as a "translator". Now, I'm thinking maybe it's time to try and help translate LMS itself.

I have loved LMS for years and can only thank the team who have been working to make it better over the years. So if I can help a little ...

In this pull request I tried to complete the French translation of all the strings.txt files. If there are other files to translate, please let me know.

I have done the best I can by trying to translate all the plugins included in this Git project. But not being a user of all the plugins myself, I hope I haven't left too many errors linked to potential misunderstandings of use.

I tried to respect the "philosophy" of the existing translation by making sure to keep the same vocabulary. It is likely that all is not perfect. Obviously, I will be able to correct this first version if errors are pointed out to me.

Best regards,
Franck

[mherger]

Thank you VERY much! There are a few minor remarks. And I actually found one spelling error 😁 .

And now I have to go back find that one string you showed me which was missing a German translation...