document or print "asset.platform" options (for k8s provider)

[DrackThor]

Is your feature request related to a problem? Please describe.
Quality of life improvement.
I am currently in the process of writing policies for k8s and I want to know which values I can use for my "asset.platform == xxx" filters.
The same might also apply for other providers I guess.

Describe the solution you'd like
I'd like to have a CLI command that can describe a provider and it's available asset types.
Maybe something like cnquery providers describe os

Describe alternatives you've considered
Alternatively also an autogenerated documentation for that provider would suffice.
Similar to the resource pack docs, eg k8s, but also containing the asset.platform info that could be found here