Webpack Valid Sourcemap Config

webpack.config.js

var path = require('path');
var webpack = require('webpack');

module.exports = {
    entry: {
        'Dashboard/index': './src/Dashboard/index.js',
    },
    output: {
        path: path.resolve(__dirname, 'dist'),
        filename: '[name].js',
    },
    module: {
        rules: [
            { test: /\.(js)$/, use: 'babel-loader' },
            { test: /\.(jsx)$/, use: 'babel-loader' }
        ]
    },
    optimization: {
        splitChunks:{
            cacheGroups: {
                vendor: {
                    test: /react|react-dom|mobx|mobx-react|moment|axios/,
                    name: "vendor",
                    chunks: "all",
                    enforce: true
                }
            }
        }
    },
    mode: "development",
    devtool: "source-map"
};