Complete French translation of the website (index, trailmap, annoncements, advisories, i18n)

[thisiskeanyvy]

• Addition of all translations for the French language (i18n, trailmap, advisories, content)
• Correction of symbols (in prologue.fr.md on lines 47;62 and 65)
• Update of translations (in about.fr.md)
• Update of menu translations (in config.toml)
• Modification of the html code to correctly display the title translations (SEO) for the French language (in head.html)
• Modification of the html code to display the translation of "Dogecoin Foundation" to "Fondation Dogecoin" -> for the French language (in index.html on lines 9; 12; 13; 14; 15 and 16)

I also propose to add some files in the .gitignore for everything that is automatically generated by npm (.hugo_build.lock and package-lock.json)