Fails silently when config not found

[kkmuffme]

When the config file isn't found, it silently fails and does nothing: https://github.com/postcss/postcss-cli/commit/b5a0c4f99b682dcf4b7401a6a5ed6398ed2ce93d

Is there a specific reason why this error is ignored @RyanZim ?

Would you accept a PR that changes this behavior that if a config path is passed (but no config found), it will still throw an error?