Update the Symfony documentation

docs/Symfony.md

@@ -5,12 +5,30 @@ Here is an example of what your `bref.php` file should contain:
 ```php
 <?php
 
+use App\Kernel;
+use Bref\Bridge\Symfony\SymfonyAdapter;
+use Symfony\Component\Debug\Debug;
+use Symfony\Component\Dotenv\Dotenv;
+
+# On lambdas the output is not displayed in the HTTP response
+ini_set('display_errors', '1');
+error_reporting(E_ALL);
+
 require __DIR__.'/vendor/autoload.php';
 
-$kernel = new \App\Kernel('prod', false);
+Debug::enable();
+
+// The check is to ensure we don't use .env in production
+if (!isset($_SERVER['APP_ENV'])) {
+    (new Dotenv)->load(__DIR__.'/.env');
+}
+if ($_SERVER['APP_DEBUG'] ?? ('prod' !== ($_SERVER['APP_ENV'] ?? 'dev'))) {
+    umask(0000);
+}
+$kernel = new Kernel($_SERVER['APP_ENV'] ?? 'dev', (bool) ($_SERVER['APP_DEBUG'] ?? ('prod' !== ($_SERVER['APP_ENV'] ?? 'dev'))));
 
 $app = new \Bref\Application;
-$app->httpHandler(new \Bref\Bridge\Symfony\SymfonyAdapter($kernel));
+$app->httpHandler(new SymfonyAdapter($kernel));
 $app->cliHandler(new \Symfony\Bundle\FrameworkBundle\Console\Application($kernel));
 $app->run();
 ```