[skotty,sksg] Initial gradient support

TBR=
Change-Id: I61e4d46ac14660f4c9ea757be2278e4098131a6b
Reviewed-on: https://skia-review.googlesource.com/94121
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 16e6819..c27af94 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1392,6 +1392,7 @@
       "experimental/sksg/geometry/SkSGRect.cpp",
       "experimental/sksg/geometry/SkSGTrimEffect.cpp",
       "experimental/sksg/paint/SkSGColor.cpp",
+      "experimental/sksg/paint/SkSGGradient.cpp",
     ]
     deps = [
       ":skia",