You may not know this, but support for ES6 was added in Drupal 8.4. It wasn't in the release notes, but I was delighted to learn of it. You have probably landed here because you have gotten the error: Cannot find module 'eslint-config-airbnb'. If you want to see ES6 linting in PHPStorm, you'll need to do a couple of things. (In order to actually use ES6 in your theme, you'll have to configure your own build transpiling task, which is out of scope here…
Read more about Drupal ES6 Linting in PhpStorm. Or, PhpStorm Drupal Error: Cannot find module 'eslint-config-airbnb'
