Extend rn_base for using twig templates instead of marker templates
It's also possible to use t3twig as template enginge for Typo3 template development insted of fluid templates.
Install TYPO3 via composer. Maybe you can use our TYPO3-Composer-Webroot Project
From project root you need to run
composer require "dmk/t3twig:~2.0"For usage please have a look in our Documentation