Lazy load bills

[magnetism2000]

We need a way to lazy load bills/issues on the all_bills_view.dart / all_issues_view.dart

Why:
There are way too many bills to show on the view at once and has huge performance issues. I think the sweet spot for my device(s10) is around 20-30 bills painted on the view at once without any performance issues. Older devices might be worse.

Possible ways:

• Add cursor to api request and recall endpoint once page is scrolled to certain point
• Store all Bills in local storage state, then call from local storage adding them to the Bill list progressively. Then call the api once per day, or on app bootup.

[KipCrossing]

This has been fixed with https://medium.com/flutter-community/flutter-widget-guide-sliverlist-widget-in-5-mins-or-less-d1215c677388

in v 0.1.2