Demo module for paragraphs

Nice. I like the fact that i can enable the demo module like this and show an example setup.
And the test can easily be based on it and has less setup work.

I do like to hear others about better examples.

And i do like to integrate some wrapping CSS in the demo output to make it (text + image, image + text) look how it should... Possibly also wrap the images with some smaller image preset. I suggest to add the CSS in a followup so that this issue is about providing default config (in replacement uf the UI process)... and the followup cares about appearance (currently requires code).

Mind some explanations here: #2414907: Ship example paragraph types

So... i like the demo concept and this start. (How can we get this issue done?)

We need inputs from the maintainer(s) on how to proceed. if further expectations exist, we can consider them for a more realistic usecase.
On positive feedback, we will provide the CSS for wrapping.

I think this demo module is enough for now, we can focus on the css later.

Commited to dev, thanks!

@miro_dietiker, will you create the new issue for the css?

Thx, done! #2445077: Provide CSS for demo module