OptionalBrailleLanguage table entries, keyed by display name -- English, 한국어, and
the rest. Passed straight back to setBrailleLanguage; MAIDR never looks
inside one.
OptionalGradeContraction grades, positional per language.
OptionalLiblouisPoints the SDK's liblouis build at the directory serving its .js,
.wasm and .data files.
The vendor SDK's braille-translation surface.
Optional, and checked at runtime rather than required: a host page may supply an older SDK build without it, and the braille line has to keep working when it does. MAIDR falls back to its own uncontracted table in that case.