Add Japanese, Korean to supported languages

[1ec5]

The list of supported languages to automatically select from should be updated to include Japanese and Korean, which are now available via the name_ja and name_ko fields in Mapbox Streets v7:

mapbox-gl-language/index.js

Line 37 in f5310b2

this.supportedLanguages = options.supportedLanguages || ['en', 'es', 'fr', 'de', 'ru', 'zh', 'ar', 'pt'];

/ref mapbox/vector-tiles#54 mapbox/mapbox-gl-native#12283 mapbox/mapbox-plugins-android#566
/cc @lukasmartinelli @eschow