Add w3c did

[ross-spencer]

E.g.:

{
  "@context": [
    "https://www.w3.org/ns/did/v1"
  ],
  "id": "did:web:kz-gedenkstaette-dachau.de",
  "verificationMethod": [
    {
      "id": "did:web:kz-gedenkstaette-dachau.de#key-1",
      "type": "Ed25519VerificationKey2020",
      "controller": "did:web:kz-gedenkstaette-dachau.de",
      "publicKeyHex": "a750d5870cc7d101292a1a87fdf7cc9ff0b3b8d2c860ae361d8efadd8bab8beb"
    },
    {
      "id": "did:web:kz-gedenkstaette-dachau.de#key-2",
      "type": "Ed25519VerificationKey2020",
      "controller": "did:web:kz-gedenkstaette-dachau.de",
      "publicKeyHex": "e7f083ba39681678fa4b841148f4e5b2e682cada4242b9aa2559b14c27bcd779"
    }
  ],
  "authentication": [
    "did:web:kz-gedenkstaette-dachau.de#key-1",
    "did:web:kz-gedenkstaette-dachau.de#key-2"
  ]
}