Overriding Drupal 8's .eslintrc.json File in Your Theme With Extends
I had to do a little RTFMing today, and so I thought I'd post about it.
First of all, this is how you set up PhpStorm to use ES6 eslint settings. You may find it useful
Is the linter getting in your way? The first way to override an eslint setting is inline, disabling it on a one-off basis.