feat: allow pulling from OCI registries

[MrMarkW]

This change enables the support of pulling charts from OCI registries using this pattern:

chart:
  name: oci://{repo-url}/{chart-name}
  version: {version}

Example:

chart:
  name: oci://public.ecr.aws/karpenter/karpenter
  version: 0.36.0

[laszlocph]

Appreciate the PR it looks good at first sight.

Let me check it and push a patch release with it.

[MrMarkW]

@laszlocph I wasn't sure where to add the documentation or a good place for a test.