Implement Cardano Transactions in explorer

[jpraynaud]

Why

We need to demonstrate the certification of the Cardano transactions in the Mithril explorer

What

Add a new Cardano Transactions tab that list the signed sets of transactions (when activated on the aggregator, see #1496) and a basic form to ask the aggregator for a proof of a subset of transactions and certificate chain verification

How

• Activate the Cardano Transactions tab when the aggregator is signing this type (and hardcode snapshot and MSD types?)
• Add the list/detail of artifacts for Cardano Transactions
• Add a form to verify a list of transactions with the WASM Mithril client
• Keep an history of the verified transactions in the local state (extra credit)