Showcase all UI elements in the demo app

[mokagio]

A key advantage of having libraries with isolated components is that we can work on them in isolation and enjoy faster build time and a smaller surface area of code to understand. Shameless plug: I write in details about this in https://increment.com/mobile/microapps-architecture/

I'd love for feature devs to work on the UI elements of this library without having to open the WordPress or WooCommerce project.

The foundation for this has already been laid, as we have an Example app in the repo with quite a few components already available.

I suggest starting from there and adding all the UI components one at a time. This would also be a great chance to:

1. Upgrade the example app to use SwiftUI, to ensure maximum future-compatibility for the UI code
2. Double check that the component is still in use, and if not, remove it instead