Posts package command event.
We want to detect packages 'require'd that have scaffold files, but are not yet allowed in the top-level composer.json file.
\Composer\Installer\PackageEvent $event: Composer package event sent on install/update/remove.
public function onPostPackageEvent(PackageEvent $event) { foreach ($this->postPackageListeners as $listener) { $listener->event($event); } }