webpack4でのreactのビルド

webpackを使って簡単なReact.jsのサンプルプログラムをビルドしてみたところ、下記のように
WARNING in webpack performance recommendations:
You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application.
と表示されビルドすることができませんでした。
webpackを触り始めたばかりで、対策方法が分かりません。
どうすればビルドできるようになるのでしょうか？
よろしくお願い致します。

> webpack-test@1.0.0 start /Users/ユーザ名/webpack-test
> webpack-dev-server

ℹ ｢wds｣: Project is running at http://localhost:9000/
ℹ ｢wds｣: webpack output is served from /
ℹ ｢wds｣: Content not from webpack is served from /Users/ユーザ名/webpack-test/public
⚠ ｢wdm｣: Hash: 93bb89bd2bb000da1d45
Version: webpack 4.16.3
Time: 5949ms
Built at: 2018-08-13 16:30:18
     Asset       Size  Chunks                    Chunk Names
 bundle.js    411 KiB       0  [emitted]  [big]  main
index.html  252 bytes          [emitted]
Entrypoint main [big] = bundle.js
[./node_modules/babel-polyfill/lib/index.js] 833 bytes {0} [built]
[./node_modules/babel-polyfill/node_modules/regenerator-runtime/runtime.js] 23.9 KiB {0} [built]
[./node_modules/react-hot-loader/patch.js] 213 bytes {0} [built]
[./node_modules/webpack-dev-server/client/index.js?http://localhost:9000] (webpack)-dev-server/client?http://localhost:9000 7.78 KiB {0} [built]
[./node_modules/webpack-dev-server/client/overlay.js] (webpack)-dev-server/client/overlay.js 3.58 KiB {0} [built]
[./node_modules/webpack-dev-server/client/socket.js] (webpack)-dev-server/client/socket.js 1.05 KiB {0} [built]
[./node_modules/webpack/buildin/global.js] (webpack)/buildin/global.js 489 bytes {0} [built]
[./node_modules/webpack/buildin/harmony-module.js] (webpack)/buildin/harmony-module.js 573 bytes {0} [built]
[./node_modules/webpack/hot sync ^./log$] (webpack)/hot sync nonrecursive ^./log$ 170 bytes {0} [built]
[./node_modules/webpack/hot/dev-server.js] (webpack)/hot/dev-server.js 1.61 KiB {0} [built]
[./node_modules/webpack/hot/log-apply-result.js] (webpack)/hot/log-apply-result.js 1.27 KiB {0} [built]
[0] multi (webpack)-dev-server/client?http://localhost:9000 (webpack)/hot/dev-server.js babel-polyfill react-hot-loader/patch ./src/index.js 76 bytes {0} [built]
[./node_modules/webpack/hot/log.js] (webpack)/hot/log.js 1010 bytes {0} [built]
[./src/components/hello.js] 738 bytes {0} [built]
[./src/index.js] 3.08 KiB {0} [built]
    + 358 hidden modules

WARNING in asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
This can impact web performance.
Assets:
  bundle.js (411 KiB)

WARNING in entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
Entrypoints:
  main (411 KiB)
      bundle.js


WARNING in webpack performance recommendations:
You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application.
For more info visit https://webpack.js.org/guides/code-splitting/
Child html-webpack-plugin for "index.html":
     1 asset
    Entrypoint undefined = index.html
    [./node_modules/html-webpack-plugin/lib/loader.js!./src/root.html] 453 bytes {0} [built]
    [./node_modules/lodash/lodash.js] 527 KiB {0} [built]
    [./node_modules/webpack/buildin/global.js] (webpack)/buildin/global.js 489 bytes {0} [built]
    [./node_modules/webpack/buildin/module.js] (webpack)/buildin/module.js 497 bytes {0} [built]
ℹ ｢wdm｣: Compiled with warnings.