The existing example is not functional, mostly because of the change from `load_orders` -> `load_orderbook`. This commit amends the example to be functional, with a small change to place the order at a value we'd typically expect to see in the orderbook representation rather than a fixed $ value, which is hopefully a bit easier for a first time user to understand when they can see their order in the orderbook.

I have kept the `print` convention of the existing example,