add "permafrost" soil

[sierra-moxon]

Looking at the subclass hiearchy under "soil" - https://www.ebi.ac.uk/ols4/ontologies/envo/classes/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FENVO_00001998?lang=en

I think we maybe missing the soil component of permafrost. Or we need to think about adding "permafrost" to the soil subclass hierarchy.

[pbuttigieg]

Permafrosts can lack soil altogether, but we can try to add a class for soil in a permafrost "state"

[timalamenciak]

I see that the existing entry for permafrost (ENVO:00000134) has one of its axioms as composed primarily of some (rock or soil or sediment). Would the reasoner not then associate that with soil? (I legitimately don't know much about how the reasoner works)

So then the subclass of soil would refer to the soil component only (not rock or sediment).

Maybe:

permafrost soil - def: Soil which is at or below the freezing point of water for two or more years

and as an axiom - part of some permafrost?

I'm happy to make this change if it addresses Sierra's comment and fits with everything.