Allowed dependency to optionally use symfony 6

Author: Sebb767

composer.json

@@ -14,7 +14,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^8.5",
-        "symfony/finder": "^3.0|^4.0|^5.0",
+        "symfony/finder": "^3.0|^4.0|^5.0|^6.0",
         "monolog/monolog": "^2.0"
     },
     "license": "MIT",