[Bug] The `--config` argument does not work when the file extension is `.hintrc`

[quisido]

🐞 Bug report

Description

If the config file uses a .hintrc file extension, hint will fail to find it and instead fallback to the built-in configuration.

Details

hint --config .production.hintrc fails to find the configuration file. ❌

hint --config hintrc.production.json finds the configuration file fine. ✅

This took me way too long to figure out why my tests were not working correctly.