Implement kubeVersion of Chart.yaml

Summary

Implement the kubeVersion field of Chart.yaml. It is an optional field that was never implemented here.

Details

https://helm.sh/docs/topics/charts/#the-chartyaml-file

Chart.yaml

apiVersion: The chart API version (required)
name: The name of the chart (required)
version: A SemVer 2 version (required)
kubeVersion: A SemVer range of compatible Kubernetes versions (optional)
description: A single-sentence description of this project (optional)
type: The type of the chart (optional)
keywords:
  - A list of keywords about this project (optional)
home: The URL of this projects home page (optional)
# ...

Explicit details on the implementation can be found in the field description, summary is that it is a SemVer range string, not explicitly a SemVer field.

For a detailed explanation of supported semver constraints see Masterminds/semver.