Abstract factory (#366)

* rewrite of the Abstract Factory pattern

* update composer deps

* fixed argument to json_encode which cannot be null

Creational/AbstractFactory/UnixJsonWriter.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace DesignPatterns\Creational\AbstractFactory;
+
+class UnixJsonWriter implements JsonWriter
+{
+    public function write(array $data, bool $formatted): string
+    {
+        $options = 0;
+
+        if ($formatted) {
+            $options = JSON_PRETTY_PRINT;
+        }
+
+        return json_encode($data, $options);
+    }
+}