Fix custom formatters access to needless disables results

[shawnbot]

Describe the issue. Is it a bug or a feature request (new rule, new option, etc.)?

I'm using a custom formatter to output logs so that our CI system can automatically create check annotations on GitHub. This works great for linting errors, but because the needless disables results are generated after the formatter is called, there's no way to access it without calling the underlying needlessDisables() function in the custom formatter.

(Side note: when I require('stylelint/lib/needlessDisables') and call it on the results in my custom formatter, things get really weird: the first (and/or last??) rule listed in my stylelint-disable comment is always reported as unused, but when I delete it the rule is applied and throws an error. 🙃)

Which version of stylelint are you using?

10.1.0

How are you running stylelint: CLI, PostCSS plugin, Node API?

CLI with stylelint --custom-formatter path/to/my/formatter.js

What did you expect to happen?

I expected the formatting function to get needlessDisables in one or more of its result objects, or as a second argument.

[alexander-akait]

Yep, looks like bad design, PR welcome