Auto-generate docs for NGF CRDs

[pleshakov]

Currently, NGF has only one CRD.
The doc for it is here https://github.com/nginxinc/nginx-gateway-fabric/blob/8612c42d8badb8e13b1baf675821350e27395c23/site/content/how-to/configuration/control-plane-configuration.md , visualized https://docs.nginx.com/nginx-gateway-fabric/how-to/configuration/control-plane-configuration/

Note how that doc describes each field of the resource.

As we add more CRDs, it will become tedious to write and maintain docs for fields. Especially considering that the source of truth (the fields + documentation for them) for documentation is go code https://github.com/nginxinc/nginx-gateway-fabric/blob/8612c42d8badb8e13b1baf675821350e27395c23/apis/v1alpha1/nginxgateway_types.go , so we will need to keep the docs in sync with the go files.

Find a way to generate docs for CRDs based on the source code.

Notes:
Example of auto-generated docs in the Gateway API -- https://gateway-api.sigs.k8s.io/reference/spec/

[kate-osborn]

Gateway API uses: https://github.com/ahmetb/gen-crd-api-reference-docs, but this is no longer maintained. There's another project that does the same thing here: https://github.com/elastic/crd-ref-docs

[kate-osborn]

@mpstefan I think we should add this to the 1.3 milestone because we will add a few new CRDs that need documentation.

[jputrino]

@lucacome @pleshakov @mpstefan -- The solution in #1884 is not in line with the tooling or format in which we (NGINX) present this information to our users. We need to discuss this and make sure solution is in line with the docs standards (ideally before work is begun).

@lucacome - Apologies, but please close your PR. We cannot sign off on publishing the API documentation in the format generated by the tooling selected.