Add Support For Kubernets 1.21 and above

[standrewd]

Description
This adds in support for Kubernetes 1.21.0 and above by adding a few tweaks to dynamically use specific version supported fields.

For versions 1.21.0 -> 1.24.0: The serviceName field is required and without it will cause the helm install to fail
For versions 1.22.0 and above: The minReadySeconds is supported and included

Testing
Validated locally using minikube against all versions between and including 1.21.0 -> 1.25.0 by doing a helm install dry run.

Documentation
No documentation needed as this is detected by the version of kubernetes.

[wfernandes]

Thanks for the quick turnaround on this @standrewd. I just left a few comments, none should be blockers.

[wfernandes]

lgtm. I left one more comment about the comment block above kubeVersion. And thanks for updating the README as well. That's a good catch.