setup a did:webvh for signing DCC credentials

[jchartrand]

Set up a did:webvh for signing DCC credentials.

Overview of did:webvh: https://didwebvh.info/latest/

did:webvh implementation guide: https://didwebvh.info/latest/implementers-guide/

We'll host it at identity.dcconsortium.org

Related issues:

Set up identity.dcconsortium.org subdomain: https://github.com/digitalcredentials/ops/issues/19