Add Composer autoloading functions and PHPStan for testing

vendor/nikic/php-parser/lib/PhpParser/ErrorHandler/Throwing.php

@@ -0,0 +1,18 @@
+<?php declare(strict_types=1);
+
+namespace PhpParser\ErrorHandler;
+
+use PhpParser\Error;
+use PhpParser\ErrorHandler;
+
+/**
+ * Error handler that handles all errors by throwing them.
+ *
+ * This is the default strategy used by all components.
+ */
+class Throwing implements ErrorHandler
+{
+    public function handleError(Error $error) {
+        throw $error;
+    }
+}