"Linked Data Signatures for GPG" https://gpg.jsld.org/

  npm i @transmute/lds-gpg2020 -g
  gpg2020 sign -u "3BCAC9A882DEFE703FD52079E9CB06E71794A713" $(pwd)/docs/example/doc.json did:btcr:xxcl-lzpq-q83a-0d5#yubikey

From https://gpg.jsld.org/contexts/#GpgSignature2020 :

> GpgSignature2020: A JSON-LD Document has been signed with GpgSignature2020, when it contains a proof field with type GpgSignature2020. The proof must contain a key signatureValue with value defined by the signing algorithm described here. Example:

  {
  "@context": [
    "https://gpg.jsld.org/contexts/lds-gpg2020-v0.0.jsonld",
    {
      "schema": "http://schema.org/",
      "name": "schema:name",
      "homepage": "schema:url",
      "image": "schema:image"
    }
  ],
  "name": "Manu Sporny",
  "homepage": "https://manu.sporny.org/",
  "image": "https://manu.sporny.org/images/manu.png",
  "proof": {
    "type": "GpgSignature2020",
    "created": "2020-02-16T18:21:26Z",
    "verificationMethod": "did:web:did.or13.io#20a968a458342f6b1a822c5bfddb584bdf141f95",
    "proofPurpose": "assertionMethod",
    "signatureValue": "-----BEGIN PGP SIGNATURE-----\n\niQEzBAABCAAdFiEEIKlopFg0L2sagixb/dtYS98UH5UFAl5JiCYACgkQ/dtYS98U\nH5U8TQf/WS92hXkdkdBQ0xJcaSkoTsGspshZ+lT98N2Dqu6I1Q01VKm+UMniv5s/\n3z4VX83KuO5xtepFjs4S95S4gLmr227H7veUdlmPrQtkGpvRG0Ks5mX7tPmJo2TN\nDwm1imm+zvJ+MXr3Ld24qaRJA9dI+AoZ5HXqNp96Yncj3oWD+DtVIZmC/ZiUw43a\nLpMYy94Hie7Ad86hEoqsdRxrwq7O6KZ29TAKi5T/taemayyXY7papU28mGjVEcvO\na7M3XNBflMcMEB+g6gjrANsgFNO6tOuvOQ2+4v6yMfpJ0ji4ta7q2d4QKqGi5YhE\nsRUORN+7HJrkmSTaT7gBpFQ+YUnyLA==\n=Uzp1\n-----END PGP SIGNATURE-----\n"
    }
  }