Improved PreviewGenerator by composing an ImageBuilder that creates new Image objects fore each URL

module/Common/src/Image/ImageBuilder.php

@@ -0,0 +1,10 @@
+<?php
+namespace Shlinkio\Shlink\Common\Image;
+
+use mikehaertl\wkhtmlto\Image;
+use Zend\ServiceManager\AbstractPluginManager;
+
+class ImageBuilder extends AbstractPluginManager implements ImageBuilderInterface
+{
+    protected $instanceOf = Image::class;
+}