Enhance and move playground into a starter template

[emmenko]

The idea is to:

• enhance the playground app (for managing state machines) to make it a more complete example of managing data in the UI
  • data fetching using rest (sdk)
  • list view and details view
  • basic form management
• move the playground into a starter template, so that people can actually download it and use it as a starter point

Furthermore, this would be really helpful for me to get feedback about the docs and the tooling.

[mmaltsev-ct]

For now, we concentrate on doing #2297 and #1668. Closing the issue.