Configuring the CSS extraction with a webpack plugin

// Load the plugin
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

// Add to config plugins
config.plugins = [    
    new MiniCssExtractPlugin()
];

// Update the css rule of the loader from using a style-loader to use our custom plugin loader.
{
    test: /\.css$/,
    use: [
        MiniCssExtractPlugin.loader,
        "css-loader"
    ]
}