i18n: add missing Spanish localization strings

[0neGal]

The Spanish localizations have become slightly outdated as the maintainer (@XNovaDelta) seems to have become MIA (?), use npm run langs:format to edit the localization files interactively...

Anyone is welcome to deal with the missing strings, and if being a maintainer for the Spanish localizations is of your interest, feel free to also edit the maintainers.json file:

cli.update.failed
gui.mods.cant_find_specific
gui.mods.cant_find_version
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.title.missing_steam
gui.toast.title.missing_flatpak
gui.toast.title.missing_flatpak_steam
gui.toast.desc.failed_to_connect
gui.toast.desc.failed_launch_command
gui.toast.desc.missing_launch_command
gui.toast.desc.missing_steam
gui.toast.desc.missing_flatpak
gui.toast.desc.missing_flatpak_steam
viper.already_running
tooltip.offline