To this point, everything you’ve done could be applied to both a “traditional” web app you’d visit on your laptop or desktop computer as well as on a mobile device. In fact, offline capabilities are likely going to be needed more often on a mobile device than on a laptop. But the web app manifest is a PWA feature that is really mobile-focused. With it, you can specify details about your app that help devices give your users the best possible experience.
Because of this, you’re going to be testing all of these features ...