Add Config per Reporter

[gossi]

I'm using codeclimate for my OSS projects. And for that to work, the code-coverage must be relative to repo-root, instead of project-root. This was easy done with the vitest project in there as it allowed to configure reports: https://vitest.dev/guide/reporters.html (it's also the same syntax that eslint uses to configure your rules).

In ember-cli-code-coverage, the config is always {} or "no config allowed". Now this PR adds support for the same config, that vitest allows.

I'm already using this with a patch on my OSS projects, here is one such PR pointed to the config.

It works, I can see my coverage on codeclimate and this PR brings back this support to everybody :)