Set up a demo website

Not sure if this is easily possible because we'd want to avoid users getting spammed through that and so on.

Maybe a video about the module would be more useful to see how it works and looks?

We can enable maillog and disable sending.
Or even use a dummy mail system without mail() call.

That's not too big deal.
With maillog you can easily visualize to-be-outgoing mails.

Assigning this to me. :-)

We decided not to do demo websites anymore. Instead we ship demo modules for simplytest.me
#2346837: Support simplytest.me
#2410115: Module: Simplenews example