Include Deprecation Notice

I started using this Helm chart before realizing that it's deprecated according to the [documentation](https://www.cockroachlabs.com/docs/stable/deploy-cockroachdb-with-kubernetes.html?filters=helm#step-2-start-cockroachdb):

> **Warning:**
> The CockroachDB Helm chart is compatible with Kubernetes versions 1.22 and earlier (the latest version as of this writing). However, no new feature development is currently planned. If you are experiencing issues with a Helm deployment on production, contact our [Support team](https://support.cockroachlabs.com/).

There should be a notice on this repository too so that people know to switch to the Operator for any new projects.

Jira issue: HELM-27

Start by locating the repository documentation for the Helm chart and compare its guidance with the linked CockroachDB documentation. Add a deprecation notice that directs new projects to the Operator, then verify that the notice is visible to users reviewing this repository.

Written by the indexing model from the issue text.