Allow to skip resources using the GVK notation

[atosatto]

This is improving the skip or reject functionality allowing to provide the full GroupVersionKind encoding for resources to be skipped.

The functionality is useful in scenarios in which specific versions of certain resources should always be rejected and/or to allow more fine-grained control of the skip logic.

Unlike the GKV encoding implemented in the upstream Kubernetes project, the APIVersion and Kind fields are separated by / to allow the concatenation of multiple arguments by ,.

[yannh]

Hey @atosatto , sorry for being a bit slow to follow with this PR. Is this linked to https://github.com/yannh/kubeconform/issues/84 ? I got thinking about the tests and now realise a good part of the diff is just reformatting :see_no_evil:

Thanks a lot for your contribution :heart:

Could you update the Readme and usage guidelines to make it clear how this would change the usage? :pray: Thanks!