Implemented writeAll and closeAll for groups

src/Group/ConnectionGroup.php

@@ -61,8 +61,20 @@ class ConnectionGroup implements EventEmitterInterface, IteratorAggregate, Count
         return $this->name;
     }
 
-    public function write(string $payload)
+    public function writeAll(string $payload)
     {
-        
+        foreach ($this->connections as $connection) {
+            if ($connection->isWritable()) {
+                $connection->write($payload);
+            }
+        }
     }
+
+    public function closeAll(string $reason, int $code=1001)
+    {
+        foreach ($this->connections as $connection) {
+            $connection->closeWithReason($reason, $code);
+        }
+    }
+
 }