Update kubekey docs for k3s installation

[lbrigman124]

Your current KubeKey version

kk version: &version.Info{Major:"3", Minor:"0", GitVersion:"v3.0.7", GitCommit:"e755baf67198d565689d7207378174f429b508ba", GitTreeState:"clean", BuildDate:"2023-01-18T01:57:24Z", GoVersion:"go1.19.2", Compiler:"gc", Platform:"linux/amd64"}

Describe this feature

Add docs and command line help that covers the k3s support for installations.

Describe the solution you'd like

Add --show-supported-k3s to version command Update docs to show that --with-kubernetes v1.24.4-k3s

Additional information

None of the information in the kubekey project other than the front page says it supports k3s and then only at the top of the readme. I knew it supported k3s installation but I had to find the options on the kubesphere docs/web pages.

There is a link to supported k3s versions but nothing showing how to enable it.