share-lt/app/Events/PreviewSiteBuilt.php

<?php

namespace App\Events;

use Illuminate\Broadcasting\Channel;
use Illuminate\Broadcasting\InteractsWithSockets;
use Illuminate\Contracts\Broadcasting\ShouldBroadcast;
use Illuminate\Foundation\Events\Dispatchable;
use Illuminate\Queue\SerializesModels;

class PreviewSiteBuilt implements ShouldBroadcast
{
    use Dispatchable, InteractsWithSockets, SerializesModels;

    public function __construct(
        public string $message = 'Preview site is built',
        public string $type = 'success'
    ) {}

    public function broadcastOn(): array
    {
        return [
            new Channel('filament-notifications'),
        ];
    }

    public function broadcastAs(): string
    {
        return 'preview-site.built';
    }
}