Add widget doc demo collection to example config

[verythorough]

- Do you want to request a feature or report a bug?
Docs feature

- What is the current behavior?
The Kitchen Sink collection in the cms-demo example config is great for testing widget code changes, and for demonstrating just how far you can go with nesting, but it's less helpful for someone learning how to configure fields on their own site. For example, the purpose of the label setting is clearer when its value doesn't match the name of the widget.

- What is the suggested behavior?
When adding config code examples to the widgets doc, I wrote them to look like common use cases. These will be even clearer when we have UI screenshots of what each config produces, and I think the example site is a great place to make the demos for that. I don't think they should replace the Kitchen Sink collection (because it serves its own purpose), but be part of a new collection, maybe "Widget Demos" or something.

After the demo config is complete, we can file an issue to take screenshots for the widget doc, or possibly track that as part of #486.

[erquhart]

I'm in total agreement with this. I originally felt that stuffing things in the example project as a form of documentation was an anti-pattern, but that was definitely incorrect. We should go the other way and start doing exactly that, providing examples of common use cases right in the example project. The kitchen sink should be retained, agreed, mostly as a stress test for the editor

We should maybe list out some specific use cases to cover here.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[martinjagodic]

Closing as stale and/or outdated.