Code cleanup, added phpstan

src/Group/GroupManager.php

@@ -4,15 +4,19 @@ namespace NoccyLabs\React\WebSocket\Group;
 
 use Evenement\EventEmitterInterface;
 use Evenement\EventEmitterTrait;
-use NoccyLabs\React\WebSocket\WebSocketInterface;
 use React\EventLoop\Loop;
-use WeakReference;
 
 class GroupManager implements EventEmitterInterface
 {
     use EventEmitterTrait;
 
+    /**
+     * @var string emitted when a new group is created
+     */
     const EVENT_CREATED = 'created';
+    /**
+     * @var string emitted after the last member leaves, when the group is destroyed
+     */
     const EVENT_DESTROYED = 'destroyed';
 
     /** @var array<string,ConnectionGroup> */