remove unused imports, add more description in readme

README.md

@@ -242,6 +242,24 @@ final class SomeController
 }
 ```
 
+Also, you can use nested groups:
+
+```yaml
+symiddleware:
+  global:
+      - App\Controller\SetCorsHeaders
+      - web
+  groups:
+    web:
+      middlewares:
+        - 'App\Middleware\ModifyRequestMiddleware'
+        - debug
+    debug:
+      if: false
+      middlewares:
+        - 'App\Middleware\LogSqlQuery'
+```
+
 Duplicated middlewares will be removed.
 
 ## Customization

src/DependencyInjection/SymiddlewareCompilerPass.php

@@ -8,7 +8,6 @@
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Psr\Http\Server\MiddlewareInterface;
 use Kafkiansky\SymfonyMiddleware\Middleware\Registry\MiddlewareRegistry;
-use Symfony\Component\DependencyInjection\Loader\Configurator\ReferenceConfigurator;
 use function Symfony\Component\DependencyInjection\Loader\Configurator\service;
 use function Symfony\Component\DependencyInjection\Loader\Configurator\service_locator;