Add a preview of the evaluated code results to the REPL output

[Duckwhale]

NodeJS has this feature where you can see the results before actually pressing ENTER, a bit like the browser console. Not sure how difficult it would be to implement a (simple) version of this, but it would be pretty neat. Should build a prototype first, though.

It's possible that this is a can of worms not opening, but it might also be much simpler than it looks. Needs research plus a POC.