Issue #3178534: Start running PHPStan on Drupal core (level 0 - part 1)

composer/Metapackage/DevDependencies/composer.json

@@ -17,6 +17,7 @@
         "justinrainbow/json-schema": "^5.2",
         "mikey179/vfsstream": "^1.6.8",
         "phpspec/prophecy": "^1.7",
+        "phpstan/phpstan": "^0.12.81",
         "phpunit/phpunit": "^8.4.1 || ^9",
         "symfony/browser-kit": "^4.4",
         "symfony/css-selector": "^4.4",