Per T108426, it would be awesome if Twinkle could be localized for wikis other than English Wikipedia. Since Twinkle is very tied to wiki-specific templates and processes, this is going to mostly involve creating an on-wiki configuration system (perhaps using JsonConfig) rather than a traditional i18n architecture. See T108426 and https://github.com/azatoth/twinkle/issues/129 for more discussion on this.
https://en.wikipedia.org/wiki/Wikipedia:Twinkle - Documentation
https://github.com/azatoth/twinkle - Code repo