Distribute Helm chart for Druid Operator

Currently, the Druid Operator Helm chart is bundled in the repository but not published in a way that users can consume with helm repo add.

To comply with [ASF Release Policy](https://www.apache.org/legal/release-policy.html?utm_source=chatgpt.com) and to make adoption easier, we should distribute the Helm chart artifacts (.tgz + index.yaml) as part of each operator release.

Inspect the bundled Druid Operator Helm chart and the operator release process first. Define how each operator release will publish the chart archive and index.yaml so users can consume them with helm repo add; done means both artifacts are available for every release.

Written by the indexing model from the issue text.