Expand and add to previous content (#24671)
Expand and add to previous content (#24671)

Notably added: origin of smart contracts, example of smart contract, references.
The added content required a slight rewording of the previous content.
I removed (miners) from "... nodes(miners) ..." since a node is not equivalent to a miner. Not all nodes are miners (and it is crucial that this is the case!!) -> https://bitcointalk.org/index.php?topic=1734235.0
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