Propagate changes in stores to subscribers

[carlosvin]

When data is changed in a store, view is not updated because stores are not react components, so we have to implement a way to propagate this changes to views, some options:

• Keep global state in upper level and pass it down through props. Use nested routes: /budgets will keep list of budget models, /budgets//expenses will keep a list of expenses in its state.
• Make stores context providers and use context values in relevant views.
• Implement a kind of subscriptions or observable pattern. We can even consider using a library like https://www.learnrxjs.io/concepts/rxjs-primer.html
• Use something like resub. Avoid resub since it doesn't support hooks and the whole app components are using them.

Interesting article about React global state management: https://www.robinwieruch.de/react-global-state-without-redux

[carlosvin]

First implementation in #88