src/vs/workbench/contrib/localization/electron-sandbox/localization.contribution.ts/LocalizationWorkbenchContribution/isLocaleInstalled
class LocalizationWorkbenchContribution:	private async isLocaleInstalled(locale: string): Promise<boolean> {
		const installed = await this.extensionManagementService.getInstalled();
		return installed.some(i => !!(i.manifest
			&& i.manifest.contributes
			&& i.manifest.contributes.localizations
			&& i.manifest.contributes.localizations.length
			&& i.manifest.contributes.localizations.some(l => locale.startsWith(l.languageId.toLowerCase()))));
	}