Improve the `waspc/example/todoApp` to be a proper kitchen sink app

[infomiho]

Today, the waspc/example/todoApp example is our main dev app which we use while developing Wasp. It contains most of Wasp's feature because over time as people built features, they first added them to that app.

Because it grew organically, it's not really organized or well designed. We want to upgrade the todoApp to be easier to navigate around with specific organization that highlight which Wasp feature is used at a certain page of the app. For example, there could be a hierarchy of pages that highlight different features:

1. Actions & queries - page where we showcase how they are used e.g. what we already have, the TODO app
2. Jobs - page where we allow users to trigger async jobs
3. CRUD - page where we showcase the CRUD feature
4. Websockets - page where we showcase the Websockets feature e.g. upgrade our chat example to look nicer

Part of this task should be enumerating which features the todoApp has, a which features it's missing. The feature matrix should help: https://docs.google.com/spreadsheets/d/1xV86yKJ_VKpcZO1QpxL_WZ7DPoyhK7rnCdcO3BHbzX0/edit?gid=0#gid=0

The organization should allow for:

1. Finding a Wasp feature
2. Testing a Wasp feature