Missing improvements before somewhat stable release

[edevosc2c]

• (Small task) Remove "PVC backup" definition: https://github.com/mviewer/helm-charts/blob/main/mviewer/templates/elasticsearch-backups-pvc.yaml: This backup mecanism should be done outside of the helm chart.
• (Big task) For all the definitions (yaml files), adapt to the new way how it is declared in the values.yaml. Compared to the original helm chart from whom it was cloned from:
  Example: .Values.elasticsearch.storage.storage_class_name to .Values.elasticsearch.persistence.es_data.storageClass
• https://github.com/pi-geosolutions/helm-charts/tree/main/mviewer
• (Small task) Document on how to push a new release like explained in https://github.com/georchestra/helm-georchestra/?tab=readme-ov-file#how-to-create-a-new-chart-release
• (Medium task) Offer the ability to customize mviewer HTML files folder (/usr/share/nginx/html). @Gaetanbrl told me at geocom that it's a bad idea, but haute loire wants it for customizing their mviewer.
  To be discussed.

Very good helm chart for having good examples on how to implement things properly: https://github.com/8gears/n8n-helm-chart/blob/main/charts/n8n/values.yaml