Add credential definition on genesis for revocation list

[noandrea]

Since revocation list credential are natively supported we need to have the credential definition existing at genesis time.

The credential definition is the following schema + vocab:

• https://github.com/elesto-dao/elesto/blob/v3.0.0-rc2/scripts/seeds/credentials/revocationList2020.schema.json
• https://github.com/elesto-dao/elesto/blob/v3.0.0-rc2/scripts/seeds/credentials/revocationList2020.context.json

What shall be used as the schema URL?

[noandrea]

scope changed