__Feature to document__ Documentation is missing for `--config` CLI option usage in [devServer docs](https://webpack.js.org/configuration/dev-server): `webpack-dev-server [--config webpack.config.js]` __Author(s)__ /cc @evilebottnawi @hiroppy __Additional information__ <!-- Please provide any additional information that is required in order to document the feature in the best possible way or say N/A if linked PR has more than enough details. --> [x] I am willing to work on this issue and submit a pull request.