This details the changes to the transaction digest algorithm for the
ZSA protocol.
- A new branch is added for hashing the information in a transaction
related to issuance.
- Some branches are added and modified in the orchard_digest subtree to
account for the additional Asset Base value that needs to be hashed.
This rearranges and rewrites various sections of the ZIP to make it more in line with the suggestions in ZIP 0.
It also updates the Split Notes, Circuit Statement and Burn Mechanism sections with more information.
This covers the changes made to derive the issuance key independently of the Orchard key structure, using the techniques from [ZIP 32](https://zips.z.cash/zip-0032).