support not-strict mode for schema validation

[eyarz]

Is your feature request related to a problem? Please describe. today, I can't add additional properties to my K8s objects because it will fail the schema step (example)

Describe the solution you'd like a flag to pass the CLI to use none strict schema for the schema validation step

Describe alternatives you've considered n/a

Additional context By default, kubeconform runs in a none strict mode. We pass the --strict flag to force the strict mode in every schema validation check.