Move Kubernetes API types to the top

[ahmetb]

Something I'm observing from my https://github.com/ahmetb/gen-crd-api-reference-docs tool that's not ported here is that this tool is showing headings for various Go types referred in my Kubernetes custom resource types on top of the page because they're alphabetically first.

I think users would much rather prefer to scan API types first, and then see some unrelated Go helper type in the page.

Is this by design, or is there room for improvement here.

[thbkrkr]

As far as I know, there's plenty of room for improvement here.