headlamp helm chart should be signed

[illume]

Artifact hub is complaining that the helm chart is not signed.

Note: there's an issue for all of our releases being signed here: https://github.com/headlamp-k8s/headlamp/issues/2092

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From the helm documentation

To sign a chart, use the '--sign' flag. In most cases, you should also provide '--keyring path/to/secret/keys' and '--key keyname'.

$ helm package --sign ./mychart --key mykey --keyring ~/.gnupg/secring.gpg

If '--keyring' is not specified, Helm usually defaults to the public keyring unless your environment is otherwise configured.

[knrt10]

Working on this