You are right.. I forgot to add the stuff you need to add to your package.json, gonna make that edit to the article, but add this as a property:

"scripts": {

"bundle": "webpack",

"test": "echo \"Error: no test specified\" && exit 1",

"start": "webpack-dev-server --mode development --open --hot",

"build": "webpack --mode production",

"check-types": "tsc"

},