add skcms_TransferFunction_isFooish()

I don't think I want to get into the business of saying whether an
skcms_Profile / SkColorSpace is "HDR", but I think we can certainly tell
you what sort of skcms_TransferFunction you're holding and let you
decide from there.

Bug: chromium:1106417
Change-Id: Iac2841b08e3f34bf2a7a089b465409115b38d42a
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/303388
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed