src/vs/workbench/contrib/localizations/browser/localizations.contribution.ts/LocalizationWorkbenchContribution/installExtension
class LocalizationWorkbenchContribution:	private installExtension(extension: IGalleryExtension): Promise<void> {
		return this.paneCompositeService.openPaneComposite(EXTENSIONS_VIEWLET_ID, ViewContainerLocation.Sidebar)
			.then(viewlet => viewlet?.getViewPaneContainer() as IExtensionsViewPaneContainer)
			.then(viewlet => viewlet.search(`@id:${extension.identifier.id}`))
			.then(() => this.extensionManagementService.installFromGallery(extension))
			.then(() => undefined, err => this.notificationService.error(err));
	}