Improve Necroparser API Reference type data

[endigo9740]

@Hugos68 feel free to flush this out further.

We were aware of a few types that weren't quite parsed as expected for the API reference. From memory:

• union types were overreaching
• snippets are primitive enough to show verbatim
• (likely more, we'll need an audit)

[Hugos68]

I might be crazy but the most simple fix would be to remove union as a typekind as a whole. Why is it there in the first place?

[endigo9740]

Why is it there in the first place?

You implemented it, I can't answer that :D