Also added debug to the example

Author: Toflar

README.md

@@ -65,7 +65,11 @@ For the Symfony 4/Flex structure, you need to adjust your `index.php` like this:
 
 // public/index.php
 $kernel = new Kernel($env, $debug);
-$kernel = new HttpCache($kernel, new Psr6Store(['cache_directory' => $kernel->getCacheDir()]));
+$kernel = new HttpCache(
+    $kernel,
+    new Psr6Store(['cache_directory' => $kernel->getCacheDir()]), [
+        'debug' => $debug,
+    ]);
 ```
 
 That's it, that's all there is to do. The `Psr6Store` will automatically