Add Symfony 6 support (#52)

Author: Quirin Stiegler

composer.json

@@ -16,17 +16,17 @@
 
     "require": {
         "php": "^7.3 || ^8.0",
-        "symfony/console": "^3.0 || ^4.0 || ^5.0",
-        "symfony/dependency-injection": "^3.0 || ^4.1.12 || ^5.0",
-        "symfony/process": "^3.0 || ^4.0 || ^5.0",
+        "symfony/console": "^3.0 || ^4.0 || ^5.0 || ^6.0",
+        "symfony/dependency-injection": "^3.0 || ^4.1.12 || ^5.0 || ^6.0",
+        "symfony/process": "^3.0 || ^4.0 || ^5.0 || ^6.0",
         "webmozart/assert": "^1.5",
         "psr/log": "^1.1"
     },
     "require-dev": {
         "ext-json": "*",
         "friendsofphp/php-cs-fixer": "^2.15",
         "phpunit/phpunit": "^8.4",
-        "symfony/framework-bundle": "^3.0 || ^4.1 || ^5.0"
+        "symfony/framework-bundle": "^3.0 || ^4.1 || ^5.0 || ^6.0"
     },
 
     "autoload": {