Let Consistency Checker Yield a Return Code

[stephanlukasczyk]

Is your suggestion for improvement related to a problem? Please describe.
I am using the consistency checker from using the jabref-action in GitHub Actions. The check result is great but I would like to see a failing CI stage if the consistency check is not successful.

Describe the solution you'd like
Usually, UNIX tools yield a non-zero return code to symbolise an error. To the best of my knowledge this also applies for GitHub Actions. Thus, I propose to add a return code (maybe optional) to the consistency check to allow the CI to fail in case of an inconsistent bib file.

[koppor]

Link to the method:

jabref/jabkit/src/main/java/org/jabref/cli/CheckConsistency.java

Line 94 in dbbc96c

checkResultWriter.writeFindings();