Use termynal.js for executable show-casing in docs
I've found this fancy feature here and thought it might suite our docs: https://github.com/ines/termynal .
This PR is just a start to add it to the
script sections (maybe even to the Tasks if we like it ;)).
To give you a small preview I attach a screenshot (however it is a nice animation supporting fast-forwarding & replay).
Let me know what you think, Peter