Process fails with `--init-rule-docs` when no docs need to be created

[TheSonOfThomp]

Running eslint-doc-generator --init-rule-docs will exit with the following error if no docs need to be created. I would expect this to be skipped in the case where nothing needs to be created.

$ eslint-doc-generator --init-rule-docs
--init-rule-docs was enabled, but no rule doc file needed to be created.
error Command failed with exit code 1.

My ideal workflow would be to always pass this flag in case there's been a rule that's been missed

[bmish]

This is an interesting point. I hadn't considered that one might want to leave this option in place indefinitely. The original idea was that this option would only be used only temporarily when intentionally creating a new rule doc, but I'm open to removing the exception so it can be used permanently.