Small additions to the locale for French

[HastagGuigui]

Feel free to correct me if I got some stuff wrong 😅

The one thing I have doubts on is POPUP_CUSTOM_PROJECT_SIZE (locales_startup.yaml), I hesitated with "resolution" but ended up sticking with size, hopefully that's still correct!

Also, French does not capitalize as much as English does (I learnt that from previous localization experience) so I fixed, like, two strings with that in mind.

I haven't added my name to the contributors in translations/README.md, if needed please credit me as "#Guigui"

[TheRealSlander]

|Also, French does not capitalize as much as English does (I learnt that from previous localization experience) so I fixed, like, two strings with that in mind.

@HastagGuigui Thanks for the contribution, I translated with capitalized word to follow exactly the original spirit of the GoZen texts, but I agree with you for the "not usual" part of this.

For the question about "resolution", I tend to precise each time I make a French translation that I will get a final view when the context will be fully known to modify what needs to be, as french is context dependent indeed.

Also, as I wasn't aware that you had pushed a translation for the new texts, I pushed them as well. My bad :D'

[voylin]

Thanks for your contribution! I've given you the contributor role in the Discord server (now you have access to the contributors blog post channel :p).

I'll add your name to the translation contributors list ;)

[HastagGuigui]

Thanks!