The complete files for the chrome extension developer article
manifest.json
background.js
style.css
popup.js
index.html
You can refer to this loom video https://www.loom.com/share/cba4503efabe4cceb3e5c29b74be47ef?sid=9fd3899d-ff43-47cd-8363-41e299b65f2d if you have trouble getting the extension being displayed