Class rename, composer add, phpUnit tests add

Rename the class from ReadEnvFile to DotEnv.
Add everything to a composer json file so it can be published to
composer repository.
Add phpUnit tests for system

vendor/nikic/php-parser/lib/PhpParser/Node/Expr/ClosureUse.php

@@ -0,0 +1,34 @@
+<?php declare(strict_types=1);
+
+namespace PhpParser\Node\Expr;
+
+use PhpParser\Node\Expr;
+
+class ClosureUse extends Expr
+{
+    /** @var Expr\Variable Variable to use */
+    public $var;
+    /** @var bool Whether to use by reference */
+    public $byRef;
+
+    /**
+     * Constructs a closure use node.
+     *
+     * @param Expr\Variable $var        Variable to use
+     * @param bool          $byRef      Whether to use by reference
+     * @param array         $attributes Additional attributes
+     */
+    public function __construct(Expr\Variable $var, bool $byRef = false, array $attributes = []) {
+        $this->attributes = $attributes;
+        $this->var = $var;
+        $this->byRef = $byRef;
+    }
+
+    public function getSubNodeNames() : array {
+        return ['var', 'byRef'];
+    }
+    
+    public function getType() : string {
+        return 'Expr_ClosureUse';
+    }
+}