Added "@return static" to "setEventManager" method interface

Author: Geolim4

src/phpFastCache/Core/Item/ExtendedCacheItemInterface.php

@@ -197,6 +197,7 @@ public function getDataAsJsonString($option = 0, $depth = 512);
      * Set the EventManager instance
      *
      * @param EventManager $em
+     * @return static
      */
     public function setEventManager(EventManager $em);
 }

src/phpFastCache/Core/Item/ItemExtendedTrait.php

@@ -368,10 +368,13 @@ public function jsonSerialize()
      * Set the EventManager instance
      *
      * @param EventManager $em
+     * @return $this
      */
     public function setEventManager(EventManager $em)
     {
         $this->eventManager = $em;
+
+        return $this;
     }