docs/book: Clusterctl

[vincepri]

/kind documentation

Describe the solution you'd like
The current clusterctl document is not in the book. We should try to port the current document and make the necessary adjustments where needed.

[kikisdeliveryservice]

hi, do you mind if i give this a try?

[vincepri]

@kikisdeliveryservice That sounds good! The content should be ported here https://github.com/kubernetes-sigs/cluster-api/blob/master/docs/book/src/tooling/clusterctl.md within the book :)