Add phpstan

Author: Prometee

composer.json

@@ -58,6 +58,7 @@
         "php-http/cache-plugin": "^1.7",
         "php-http/mock-client": "^1.2",
         "php-http/promise": "^1.0",
+        "phpstan/phpstan": "^1.11",
         "symfony/browser-kit": "^5.4 || ^6.0 || ^7.0",
         "symfony/cache": "^5.4 || ^6.0 || ^7.0",
         "symfony/dom-crawler": "^5.4 || ^6.0 || ^7.0",