cardano-ledger-api documentation on adding Data to TxOut

Add documentation with Haddock examples using doctests in `Cardano.Ledger.Api.Tx.Out` on how to create a `TxOut` with `DatumHash` and inline datum. We should also show how to add a supplemental datum hash (a datum added in the transaction body which is not needed for script execution, but must refer to a datum hash in one of the transaction outputs) and what happens if no transaction output refers to that supplemental datum hash.