Support abstract and headline

[sync-by-unito]

Gitbook: https://docs.numbersprotocol.io/introduction/numbers-protocol/defining-web3-assets/assettree

• caption (already existed) => abstract
• headline (need to implement) => headline

The registration API should allow users to write abstract and headline. Whenever user updates the caption or headline, there should be a new commit to update the asset tree. Users will be charged for 0.1 NUM to upgrade the on-chain information.

┆Issue is synchronized with this Asana task by Unito
┆Created By: Tammy Yang