Lattice

Lattice generates JSON dictionaries + a strongly-typed accessor from a single source of truth. Zero runtime. Zero dependencies. Tree-shakable. Used in production at three different startups I know of. I built it for my own freelance work and the README is what I'm proudest of. The tool is small (under 1k lines) but the docs are 50 pages. I'm leaving it because I joined a company that uses a different i18n solution and I can't ethically maintain both.