Add support for config file (`cosmiconfig`) like in other tools

[dartess]

Storing settings in an string of cli command is not always convenient.
It would be great to be able to separate the config into a file, as it works for Babel or Prettier.
There is a tool for this: https://www.npmjs.com/package/cosmiconfig.
I'm ready to make a PR if the author of the repository likes the idea and takes the time to review it.