-fail-on-error is deprecated.
https://github.com/reviewdog/reviewdog/blob/master/CHANGELOG.md#rotating_light-deprecation-warnings

However, this workflow depends on reviewdog/action-suggester, which does not support -fail-level.

Until the action-suggester is improved, I focus on backward compatibility and set the default value to -fail-on-error at #80.

Once the action-suggester is improved, we will delete the default value.
Related to: reviewdog/action-suggester#64