Added callback comment for callback argument

Author: Geolim4

lib/Phpfastcache/Helper/CacheConditionalHelper.php

@@ -50,6 +50,7 @@ public function get(string $cacheKey, callable $callback, $expiresAfter = null)
         $cacheItem = $this->cacheInstance->getItem($cacheKey);
 
         if (!$cacheItem->isHit()) {
+            /** Parameter $cacheItem will be available as of 8.0.6 */
             $cacheItem->set($callback($cacheItem));
             if ($expiresAfter) {
                 $cacheItem->expiresAfter($expiresAfter);