Add a 2d cross product intrinsic to sksl

Change-Id: Iebaf4616665547d6ca4900e1247d5b68e0f3512a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/321790
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
5 files changed