feat: initial release of relaticle/comments

Filament comments package with:
- Polymorphic commenting on any Eloquent model
- Threaded replies with configurable depth
- @mentions with autocomplete and user search
- Emoji reactions with toggle and who-reacted tooltips
- File attachments via Livewire uploads
- Reply and mention notifications via Filament notification system
- Thread subscriptions for notification control
- Real-time broadcasting (opt-in Echo) with polling fallback
- Dark mode support
- CommentsAction, CommentsTableAction, CommentsEntry for Filament integration
- 204 tests, 421 assertions

src/Events/UserMentioned.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Relaticle\Comments\Events;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Foundation\Events\Dispatchable;
+use Illuminate\Queue\SerializesModels;
+use Relaticle\Comments\Comment;
+
+class UserMentioned
+{
+    use Dispatchable;
+    use SerializesModels;
+
+    public function __construct(
+        public readonly Comment $comment,
+        public readonly Model $mentionedUser,
+    ) {}
+}