create topic domain section within SPLASH

[abotzki]

from @ppalagi
We should have as well in SPLASH a section that can be called FAIR Training that could contain resources like this guide (and the FAIR Training Handbook, and the FAIR training material by design). We need a shared space where we can collect these resources by topics (a topic is FAIR training for instance) that we produced in ELIXIR, and show them to the world!