Hi there! First of all, thanks to all the contributors for this awesome project. Having all the tools, configuration and setup in one place helps tons.
create-react-app doesn't have any CSS linting yet. I noticed that there was tentative agreement for further consideration in https://github.com/facebookincubator/create-react-app/issues/636#issuecomment-246687341, so I decided to open a PR for this, since I need it for a project anyway.
I've included the standard config because I don't have a full opinionated stylelint config yet, but this can of course be changed.
Note: This depends on my fork of @vieron's stylelint webpack plugin, because the errors were not displaying correctly using watch mode in CRA. I've opened a pull request on the plugin here: vieron/stylelint-webpack-plugin#43
Edit: Pull request has been merged!