add support for image pull secrets

[rajsameer]

Summary

Adds optional imagePullSecrets support to the prometheus-openstack-exporter Helm chart, allowing the deployment to pull images from private container registries that require
authentication.

Changes

• templates/deployment.yaml: Conditionally renders imagePullSecrets in the Pod spec when values are provided.
• values.yaml: Adds imagePullSecrets field (empty list by default) with a commented example showing usage.

Usage

To use a private registry, set imagePullSecrets in your values.yaml or via --set:

imagePullSecrets:
- name: my-registry-secret

Notes

• Fully backwards compatible — defaults to an empty list, so existing deployments are unaffected.
• Follows the standard Kubernetes imagePullSecrets spec format.