New: Exit on fatal error (fixes #13711)

[A-Katopodis]

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What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
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[ ] Add autofixing to a rule
[ ] Add a CLI option
[x] Add something to the core
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What changes did you make? (Give an overview)

Created a new feature which enables ESLint to exit with code 2 instead of 1 when there are any fatal errors. More on this feature can be found in the RFC.

Is there anything you'd like reviewers to focus on?

The unit test coverage remained the same. The docs where updated as well but the only appropriate change or place to mention the new argument I found was in command-line-interface.md. Let me know if there are places I missed.

[eslint-github-bot]

Hi @A-Katopodis!, thanks for the Pull Request

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[nzakas]

This looks like a good start. I left a few suggestions. I think if you rebase on top of master then you’ll fix the linting errors in CI

[nzakas]

LGTM. Thanks!

[nzakas]

@A-Katopodis we'd like to thank you for your work on this PR. Can you shoot me an email at contact (at) eslint (dot) org?

[mdjermanovic]

Looks good, I left just some small suggestions about documentation and test descriptions.

[nzakas]

@A-Katopodis can you take a look at the latest review comments?

[mdjermanovic]

LGTM, thanks!