Add `Tx -> hash`

[alekswithakayy]

The Tx type is currently missing a hash field.

[SebastienGllmt]

My understanding is that this is resolved (the cardano.Tx object now has a hash field)

[Mercurial]

This has been resolved. The hash field now exists in the Tx message as field 13:

bytes hash = 13; // Hash of the transaction that serves as main identifier

Closing as completed.