How to properly process css file in webpack 4 loader + mini-extract-css-plugin?

Question

webpack

There is a simple config for webpack 4

const path = require('path');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
    entry: {
        app: './src/index.js',
    },
    output: {
        filename: '[name].js',
        path: path.resolve(__dirname, './dist'),
        publicPath: '/dist',
    },
    plugins: [
        new MiniCssExtractPlugin({
            filename: '[name].css',
        })
    ],
    module: {
        rules: [
            {
                test: /\.js$/,
                loader: 'babel-loader',
                exclude: '/node_modules/'
            },
            {
                test: /\.css$/,
                use: [
                    MiniCssExtractPlugin.loader,
                    'css-loader'
                ],
            },
        ],
    },
    devServer: {
        overlay: true,
    },
}

The css file is imported into the entry point (index.js), it is necessary to output it in the production assembly to a separate main.css file (using the mini-css-extract-plugin). But there is an error

Here is the complete file structure