Pass docker.secrets using skaffold init

Is it possible to pass `docker.secrets` as part of the `--artifact` payload into the generated YAML file when using `skaffold init`?

I was hoping something like this would work, but the payload keys don't seem to match the Skaffold config file keys.

```
skaffold init \
--artifact '{"image":"run","builder":"Docker","payload":{"path":"Dockerfile","secrets":[{"id":"google_application_credentials","src":"/Users/josh/.config/gcloud/application_default_credentials.json"}]}}'
--kubernetes-manifest pods_and_services.yaml
--filename skaffold.yaml
--force
```

The keys allowed in the JSON payload don't seem to be well-documented.

For more context, I'm trying to understand how to pass build-time secrets using Cloud Code VSCode plugin: https://github.com/GoogleCloudPlatform/cloud-code-vscode/issues/848