[README] Add DebugBundle to the list

Author: Edvinas Klovas

README.md

@@ -53,6 +53,9 @@ It comes pre-configured with the following bundles:
   * [**SensioGeneratorBundle**][13] (in dev/test env) - Adds code generation
     capabilities
 
+  * **DebugBundle** (in dev/test env) - Adds Debug and VarDumper component
+    integration
+
 All libraries and bundles included in the Symfony Standard Edition are
 released under the MIT or BSD license.