fix phpdoc

Author: QuentinGab

.gitignore

@@ -1,3 +1,4 @@
+**/.DS_Store
 .idea
 .phpunit.result.cache
 build

src/Concerns/ParticipateToConversations.php

@@ -7,6 +7,7 @@
 use Elegantly\Conversation\Conversation;
 use Elegantly\Conversation\ConversationUser;
 use Elegantly\Conversation\Message;
+use Illuminate\Database\Eloquent\Collection;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Database\Eloquent\Relations\HasOne;