Feat: Setup `Bloc` in `App`

[nelsonic]

As noted in #320 (comment), we have done a decent amount of research 🔍
into Bloc for state management in a Flutter App 📱
and created https://github.com/dwyl/flutter-bloc-tutorial to capture our learning. 📝

The conclusion is:while it definitely adds "boilerplate" code to the App,
it improves organisation and testability because the state of all widgets.

Todo

• Port the code from flutter-bloc-tutorial to the App. 🧑‍💻
• Link to the the tutorial in the README.md > How? section. ❓
  • Add Coverage badge to README.md so we know the initial tests are covering the new code. 💯
• Create PR.