Should not fail on info findings

[PascalTurbo]

• [] This is a bug report
• This is a feature request
• I searched existing issues before opening this one

Expected behavior

Hadolint should not fail (Return Code != 0) if only findings with severity "info" are found.

Actual behavior

Hadolint fails also on info findings what makes it nearly useless in a CI/CD Setup (where we want to stop the pipeline on warnings but not on info severities)

A possible solution would be to add an option to set on which severities it should fail.