Draft: Add new "attestation verify" command

There's something wrong with how I installed sigstore-go that caused a full rewrite of the mod files 🤷 but overall it works, see below.

Output;

make && bin/glab attestation verify
{
   "mediaType": "application/vnd.dev.sigstore.verificationresult+json;version=0.1",
   "signature": {
      "certificate": {
         "certificateIssuer": "CN=sigstore-intermediate,O=sigstore.dev",
         "subjectAlternativeName": "https://github.com/sigstore/sigstore-js/.github/workflows/release.yml@refs/heads/main",
         "issuer": "https://token.actions.githubusercontent.com",
         "githubWorkflowTrigger": "push",
         "githubWorkflowSHA": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1",
         "githubWorkflowName": "Release",
         "githubWorkflowRepository": "sigstore/sigstore-js",
         "githubWorkflowRef": "refs/heads/main",
         "buildSignerURI": "https://github.com/sigstore/sigstore-js/.github/workflows/release.yml@refs/heads/main",
         "buildSignerDigest": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1",
         "runnerEnvironment": "github-hosted",
         "sourceRepositoryURI": "https://github.com/sigstore/sigstore-js",
         "sourceRepositoryDigest": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1",
         "sourceRepositoryRef": "refs/heads/main",
         "sourceRepositoryIdentifier": "495574555",
         "sourceRepositoryOwnerURI": "https://github.com/sigstore",
         "sourceRepositoryOwnerIdentifier": "71096353",
         "buildConfigURI": "https://github.com/sigstore/sigstore-js/.github/workflows/release.yml@refs/heads/main",
         "buildConfigDigest": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1",
         "buildTrigger": "push",
         "runInvocationURI": "https://github.com/sigstore/sigstore-js/actions/runs/4735384265/attempts/1"
      }
   },
   "verifiedTimestamps": [
      {
         "type": "Tlog",
         "uri": "https://rekor.sigstore.dev",
         "timestamp": "2023-04-19T05:45:12+12:00"
      }
   ],
   "verifiedIdentity": {
      "subjectAlternativeName": {
         "subjectAlternativeName": "",
         "regexp": "^https://github.com/sigstore/sigstore-js/"
      },
      "issuer": {
         "issuer": "https://token.actions.githubusercontent.com"
      }
   },
   "statement": {
      "_type": "https://in-toto.io/Statement/v0.1",
      "subject": [
         {
            "name": "pkg:npm/sigstore@1.3.0",
            "digest": {
               "sha512": "76176ffa33808b54602c7c35de5c6e9a4deb96066dba6533f50ac234f4f1f4c6b3527515dc17c06fbe2860030f410eee69ea20079bd3a2c6f3dcf3b329b10751"
            }
         }
      ],
      "predicateType": "https://slsa.dev/provenance/v0.2",
      "predicate": {
         "buildType": "https://github.com/npm/cli/gha/v2",
         "builder": {
            "id": "https://github.com/actions/runner"
         },
         "invocation": {
            "configSource": {
               "digest": {
                  "sha1": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1"
               },
               "entryPoint": ".github/workflows/release.yml",
               "uri": "git+https://github.com/sigstore/sigstore-js@refs/heads/main"
            },
            "environment": {
               "GITHUB_EVENT_NAME": "push",
               "GITHUB_REF": "refs/heads/main",
               "GITHUB_REPOSITORY": "sigstore/sigstore-js",
               "GITHUB_REPOSITORY_ID": "495574555",
               "GITHUB_REPOSITORY_OWNER_ID": "71096353",
               "GITHUB_RUN_ATTEMPT": "1",
               "GITHUB_RUN_ID": "4735384265",
               "GITHUB_SHA": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1",
               "GITHUB_WORKFLOW_REF": "sigstore/sigstore-js/.github/workflows/release.yml@refs/heads/main",
               "GITHUB_WORKFLOW_SHA": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1"
            },
            "parameters": {}
         },
         "materials": [
            {
               "digest": {
                  "sha1": "dae8bd8eb433a4147b4655c00fe73e0f22bc0fb1"
               },
               "uri": "git+https://github.com/sigstore/sigstore-js@refs/heads/main"
            }
         ],
         "metadata": {
            "buildInvocationId": "4735384265-1",
            "completeness": {
               "environment": false,
               "materials": false,
               "parameters": false
            },
            "reproducible": false
         }
      }
   }
}