Link to GitHub Actions workflow that produced a signature

[imjasonh]

This is the information in the cert for https://rekor.tlog.dev/?logIndex=2702284:

This gives enough information to link to the workflow definition that produced the image, down to the exact commit:
https://github.com/distroless/static/blob/78ca42f54a60dd38c67201c7437d8df2b4bde2a9/.github/workflows/release.yaml