Improve app architecture

## Overview

The [Model-View-ViewModel](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93viewmodel) architecture pattern is a good way to "separate the user interface from the backend logic". This also allows for the backend to be easily tested on its own without it being tightly coupled with the UI.

### Repository pattern

Additionally, a repository pattern can be used where the logic used to retrieve data can be separated from the ViewModel. Google recommends such a pattern as part of the [Guide to app architecture docs](https://developer.android.com/jetpack/guide#recommended-app-arch).

## Current progress

- [ ] Todos _(in progress)_
- [x] Help page