Add Symfony 6.0 support (#24)

Author: PabloKowalczyk

composer.json

@@ -24,9 +24,9 @@
     },
     "require": {
         "php": ">=7.4",
-        "symfony/config": "^4.4 || ^5.4",
-        "symfony/dependency-injection": "^4.4 || ^5.4",
-        "symfony/http-kernel": "^4.4 || ^5.4"
+        "symfony/config": "^4.4 || ^5.4 || ^6.0",
+        "symfony/dependency-injection": "^4.4 || ^5.4 || ^6.0",
+        "symfony/http-kernel": "^4.4 || ^5.4 || ^6.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.4"