Crear un controlador frontend en Magento 2

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:App/etc/routes.xsd">
    <router id="standard">
        <route id="gdwhello" frontName="gdwhello">
            <module name="GDW_Hello"/>
        </route>
    </router>
</config>

<?php
namespace GDW\Hello\Controller\Index;

use Magento\Framework\App\Action\Action;
use Magento\Framework\App\Action\Context;
use Magento\Framework\Controller\ResultFactory;

class Index extends Action
{
    public function __construct(Context $context)
    {
        parent::__construct($context);
    }

    public function execute()
    {
        $result = $this->resultFactory->create(ResultFactory::TYPE_RAW);
        $result->setContents('Hola desde Magento 2');
        return $result;
    }
}