webpack-dev-server warning on npm start

Created by: robcaldecott

This is not a bug but it might need someone knowledgeable in the CRA webpack config to take a look.

Since 1.0.15 running npm start will generate the following console message:

The `setup` option is deprecated and will be removed in v3. Please update your config to use `before`

This warning is coming from the webpack-dev-server module and is in danger of confusing users. The issue is caused by the use of the packages/react-scripts/config/webpackDevServer.config.js setup function (line 98.)

More info here:

https://webpack.js.org/configuration/dev-server/#devserver-setup

I do not know if simply moving the code from setup to before will be enough to address this.