i18n: add new localization strings

[0neGal]

As always, a PR will do, localizing the new strings in the respective languages, use npm run langs:format to edit the localization files interactively...

gui.browser.sort.newest
gui.browser.sort.last_updated
gui.browser.sort.highest_rating
gui.browser.sort.most_downloads
gui.toast.title.failed_to_connect
gui.toast.desc.failed_to_connect
tooltip.offline

• German - @DxsSucuk
• French - @Alystrasz
• Chinese - @KenMizz
• Spanish - new maintainer possibly needed
  • i18n: add missing Spanish localization strings #256