Add EmailEditor page into MailPoet admin

[MAILPOET-5603]

mailpoet/lib/AdminPages/Pages/EmailEditor.php

@@ -0,0 +1,20 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\AdminPages\Pages;
+
+use MailPoet\AdminPages\PageRenderer;
+
+class EmailEditor {
+  /** @var PageRenderer */
+  private $pageRenderer;
+
+  public function __construct(
+    PageRenderer $pageRenderer
+  ) {
+    $this->pageRenderer = $pageRenderer;
+  }
+
+  public function render() {
+    $this->pageRenderer->displayPage('email_editor.html', []);
+  }
+}