Add randomness demo. Add section about splitting consumption and reveal of random number.

[architect-dev]

Randomness demo: https://github.com/FhenixProtocol/rng-binary-guessing-game-demo

Sorry about the formatting changes my ide gets a little overzealous 👍

[eshelB]

Interesting idea with the split between consumption and reveal, hadn't thought about it.

However, I think maybe there has to be another mechanic to prevent this: a contract calls both consume and reveal in the same transaction, and then reverts it if the result is undesirable.

maybe something like saving the current block in the consume, and then checking the reveal didn't occur in the same block

[architect-dev]

Yeah you're absolutely right it needs to check that the block has progressed. I've just committed an update that fixes it.