Update demo for React 17 and hooks "way of thinking"

[Svish]

Please provide us with the following information:

This issue is for a: (mark with an x)

- [ ] bug report -> please search issues before submitting
- [x ] feature request
- [x ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)

Expected/desired behavior

The current demo/sample is rather outdated and messy (in my opinion). Would be very helpful if the demo was cleaned up and written more "hooks-friendly". If at all possible, things should also be done without having to wrap the whole application in a HOC.