Update README.md

Author: marcreichel

README.md

@@ -69,6 +69,13 @@ return [
      * To turn cache off set this value to 0
      */
     'cache_lifetime' => env('IGDB_CACHE_LIFETIME', 3600),
+    
+    /**
+     * The prefix used to cache the results.
+     *
+     * E.g.: `[CACHE_PREFIX].75170fc230cd88f32e475ff4087f81d9`
+     */
+    'cache_prefix' => 'igdb_cache',
 
     /*
      * Path where the webhooks should be handled.