Update dependency phpstan/phpstan to v2 (#31)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

composer.json

@@ -15,7 +15,7 @@
     },
     "require-dev": {
         "dealerdirect/phpcodesniffer-composer-installer": "^1.0",
-        "phpstan/phpstan": "^1.7",
+        "phpstan/phpstan": "^2.0",
         "phpunit/phpunit": "^9 || ^10 || ^11",
         "squizlabs/php_codesniffer": "^3.7"
     },