The Superbrave coding standards uses some existing standards combined, with a few exceptions.

For more details about a custom code guideline, see https://github.com/squizlabs/PHP_CodeSniffer/wiki/Coding-Standard-Tutorial

When using these coding standards through composer, modify the following files:

composer.json

"require-dev" : {
  "superbrave/coding-standards": "dev-master"
}

phpcs.xml

<?xml version="1.0"?>
<ruleset>
  <rule ref="vendor/superbrave/coding-standards/Superbrave"/>
</ruleset>

Don't forget to run a composer update after editing the composer.json file.