Implementation of UnitConverter

Dear community,

I would like to implement UnitConverter and its related classes in Foundation.
I didn't find any related task so I created one (SR-2039 <https://bugs.swift.org/browse/SR-2039&gt;\).
Is it okay to assign to myself?
Is there any reason for which it should not be implemented yet?

Regards,
Alfredo Delli Bovi