DI + Navigation + ViewModel

[sdsantos]

• Stored dependencies in the App instance of each platform, so they can be reused if we want to
• Setup Jetpack Navigation
• Setup ViewModels with the androidx ViewModel
• Example ViewModel with a single state and onEvent method approach
• Updated the README to better reflect our goals

All of patterns used are still up for discussion, just went with the approach I'm using in my latest projects, and with the underlying goal of making our code consistent and easily testable.

Closes #7, #8 and #9

[aanorbel]

🐳