Improve kyaml documentation

kyaml has a decent amount of auto-generated Go documentation here: https://pkg.go.dev/sigs.k8s.io/kustomize/kyaml

Still, there's room for improvement, particularly in terms of adding examples.

The documentation on extending Kustomize should also mention kyaml and at least link to relevant examples in the Go docs.

The kyaml root directory should also have a basic README

/area kyaml
/kind documentation
/triage accepted

Start with the kyaml Go documentation at pkg.go.dev, the existing documentation on extending Kustomize, and the kyaml root directory. Identify suitable examples to add or link, update the Kustomize guidance to mention kyaml, and provide a basic kyaml README.

Written by the indexing model from the issue text.