feat(extraObjects): Add support for additioanl K8S objects

[Mart-Kuc]

PR for #726

Add support for extra K8S objects.

[Momotoculteur]

That would be awesome to have a folder CI in our chart, and have some scenario to execute in CI, like this chart for example :
https://github.com/prometheus-community/helm-charts/tree/main/charts/kube-prometheus-stack/ci
https://github.com/prometheus-community/helm-charts/blob/main/charts/kube-prometheus-stack/ci/01-provision-crds-values.yaml

It's pretty hard to see the rendering behind the manifest_extra.yaml if we have really our format we want like :

  # - apiVersion: velero.io/v1
  #   kind: Schedule
  #   metadata:
  #     name: weblate-backup
  #   spec:
  #     schedule: "0 2 * * *"
  #     template:
  #       includedNamespaces:
  #         - weblate

Some chart has more complex template like https://github.com/prometheus-community/helm-charts/blob/main/charts/kube-prometheus-stack/templates/extra-objects.yaml

[Momotoculteur]

Just made a pr for the same topic, but for jenkins helm chart, if you want to have a look : jenkinsci/helm-charts#1593