Move plugin files to a subfolder

[MAILPOET-3988]

mailpoet/lib/Util/pQuery/Html5Parser.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace MailPoet\Util\pQuery;
+
+use MailPoetVendor\pQuery\Html5Parser as pQueryHtml5Parser;
+
+class Html5Parser extends pQueryHtml5Parser {
+  /** @var string|DomNode */
+  public $root = DomNode::class;
+}