TestContextualLink.php

<?php

namespace Drupal\menu_test\Plugin\Menu\ContextualLink;

use Drupal\Core\Menu\ContextualLinkDefault;
use Symfony\Component\HttpFoundation\Request;

/**
 * Defines a contextual link plugin with a dynamic title from user input.
 */
class TestContextualLink extends ContextualLinkDefault {
    
    /**
     * {@inheritdoc}
     */
    public function getTitle(Request $request = NULL) {
        return "<script>alert('Welcome to the jungle!')</script>";
    }

}