Update the french version

[vjousse]

Review and update the content of the french version to be sure that everything is still relevant in 2024.

Will fix #18

• Add Neovim aparté
• Review introduction
• Use up to date solarized theme https://github.com/ericbn/vim-solarized
• Consider showcasing the Nerdtree font rendering with fern using https://github.com/lambdalisue/vim-fern-renderer-nerdfont ?
• Check usefulness of Lusty* plugins compared to LeaderF for example
• Check behavior on windows and WSL
• Change code links to 2024 branch
• Check code-highlighting in PDF
• Check `` rendering in PDF https://stackoverflow.com/questions/10870719/inline-code-highlighting-in-restructuredtext ? https://stackoverflow.com/questions/13530489/adding-background-color-of-notes-to-sphinx-generated-pdf-files