Limited ISO 639-1 support.
LanguageCode
type LanguageCode = AA
| AB
| AF
| AK
| AM
| AN
| AR
| BA
| BE
| BG
| BN
| CA
| CS
| DE
| EL
| EN
| ES
| FR
| GD
| GL
| HI
| HY
| JV
| KO
| MR
| MS
| NO
| PA
| PL
| PS
| PT
| QU
| RM
| RN
| RO
| RU
| SQ
| SR
| SV
| TA
| TH
| TR
| UG
| UK
| UR
| UZ
| VE
| VI
| VO
| WA
| WO
| XH
| YI
| YO
| ZA
| ZH
| ZU
fromString : String -> Maybe LanguageCode
toString : LanguageCode -> String