[canvaskit] Expose parseColorString

This is handy for interacting with <input type=color>

Change-Id: I7946c08ef10a2481016885d58cc52f76f5cd40e7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/272344
Reviewed-by: Kevin Lubick <kjlubick@google.com>
5 files changed