Add phpstan script

[dependabot skip]

Author: swissspidy

composer.json

@@ -93,11 +93,13 @@
         "lint": "run-linter-tests",
         "phpcs": "run-phpcs-tests",
         "phpcbf": "run-phpcbf-cleanup",
+        "phpstan": "run-phpstan-tests",
         "phpunit": "run-php-unit-tests",
         "prepare-tests": "install-package-tests",
         "test": [
             "@lint",
             "@phpcs",
+            "@phpstan",
             "@phpunit",
             "@behat"
         ]