Update PHP-CS-Fixer cache path and add PHPStan command

Changed the cache path in `.php-cs-fixer.dist.php` to improve organization by moving it to the `var` directory. Added a new Composer script for running PHPStan to streamline static analysis workflows.

.php-cs-fixer.dist.php

@@ -25,7 +25,7 @@ $config = new PhpCsFixer\Config();
 $config
     ->setFinder($finder)
     ->setRiskyAllowed(true)
-    ->setCacheFile('.cache/php-cs-fixer.cache')
+    ->setCacheFile('var/php-cs-fixer.cache')
     ->setUsingCache(true)
     ->setParallelConfig(PhpCsFixer\Runner\Parallel\ParallelConfigFactory::detect())
 ;