public function copyProjectExtraFiles(Event $event): void
    {
        $extras = $event->getComposer()->getPackage()->getExtra();
        if (array_key_exists('copy-files', $extras)) {
            $this->installer->getIo()->write(
                sprintf('  - Copied additional file(s)'),
                true
            );
            $this->copyExtras($extras['copy-files']);
        }
    }