Add Composer autoloading functions and PHPStan for testing

vendor/nikic/php-parser/grammar/tokens.template

@@ -0,0 +1,17 @@
+<?php
+$meta #
+#semval($) $this->semValue
+#semval($,%t) $this->semValue
+#semval(%n) $this->stackPos-(%l-%n)
+#semval(%n,%t) $this->stackPos-(%l-%n)
+
+namespace PhpParser\Parser;
+#include;
+
+/* GENERATED file based on grammar/tokens.y */
+final class Tokens
+{
+#tokenval
+    const %s = %n;
+#endtokenval
+}