Generate xmldoc descriptions for enum values

[xPaw]

For example, SHChangeNotify adds SHCNE_ID and SHCNF_FLAGS enums, but neither the enum itself or the values have any xmldocs.

I don't know if the metadata for these exists, but it's documented at least: https://learn.microsoft.com/en-us/windows/win32/api/shlobj_core/nf-shlobj_core-shchangenotify

[AArnott]

The challenge here is that there is no machine-parseable, consistently formated place to get these docs. Each enum's values may or may not be individually documented, and often the docs are scattered across docs.microsoft.com. I don't think we have xml docs for any enum values.
Any improvement we can make in this area will be in the win32metadata repo, where the docs get scraped. I'll move the issue. But ... don't hold your breath as I don't think we'll be able to fix this. docs.microsoft.com continues to be your source for some docs.