Adding the sha256 checksum into stat

[eulerjiang]

The json result from api query also contain sha256 in checksum check, if sha256 checksum is enabled in Artifactory server.

Kuberenete helm repo also use the sha256 checksum in the index.yaml to verify the chart packages. :If use Artifactory to host helm repo, the sha256 checksum can be used during helm repo index.yaml update.

[TechnicalPirate]

Would be great to see this change merged 👍