feat: add `digest` field to `Artifact` struct

[0x416e746f6e]

Github API sends digest field (sha256 sum) with responses to calls at /repos/{owner}/{repo}/actions/runs/{run_id}/artifacts (see: https://docs.github.com/en/rest/actions/artifacts?apiVersion=2022-11-28):

{
  "total_count": 2,
  "artifacts": [
    {
      "id": 11,
      // ...
      "digest": "sha256:cfc3236bdad15b5898bca8408945c9e19e1917da8704adc20eaa618444290a8c",
      // ...
    },
    // ...
  ]
}

It would be great to have the digest in golang struct as well (for example, to verify the integrity of the downloaded artifact).

[gmlewis]

Would you like to work on this issue, or shall we open this up to other amazing contributors to this repo?

[0x416e746f6e]

Would you like to work on this issue, or shall we open this up to other amazing contributors to this repo?

please open it up @gmlewis