src/vs/platform/localizations/node/localizations.ts/LocalizationsService/getLanguageIds
class LocalizationsService:	getLanguageIds(): Promise<string[]> {
		return this.cache.getLanguagePacks()
			.then(languagePacks => {
				// Contributed languages are those installed via extension packs, so does not include English
				const languages = ['en', ...Object.keys(languagePacks)];
				return distinct(languages);
			});
	}