Include raw twig template

IncludeRawExtension.php

<?php

class IncludeRawExtension extends \Twig_Extension
{
    public function getFunctions()
    {
        return [
            new \Twig_SimpleFunction(
                'includeRaw',
                [$this, 'includeRaw'],
                ['needs_environment' => true, 'is_safe' => ['html']]
            ),
        ];
    }

    public function includeRaw(\Twig_Environment $env, $template)
    {
        return $env->getLoader()->getSource($template);
    }

    public function getName()
    {
        return 'include_raw';
    }
}