Add tutorials/demos

[snazy]

Add some Nessie tutorials for Katacoda.
There's already some WIP.

[snazy]

See projectnessie/nessie#1121
See projectnessie/nessie#1120

[snazy]

Katacoda turned out to a a quite buggy organization management (clear-text web hook secrets visible to all org members, every org member can convert every org member to an org, every org member can edit every org and org member's attributes, email address changes aren't verified, etc, etc, etc), setting-up environments sometimes never succeed and finally their support is rather non existent.

Maybe Instruqt is a better alternative, but we'd need to invest a bit more time on that one.

[omarsmak]

Is this still valid?

[snazy]

Nope, closed