[svg] Implement feOffset filter

https://www.w3.org/TR/SVG11/filters.html#feOffsetElement

We should now be passing filters-felem-02-f W3C test.

Bug: skia:10841
Change-Id: I642cf3c8816b83bdf88066c55103e432ae9c9d5a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/354216
Commit-Queue: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
diff --git a/modules/svg/include/SkSVGNode.h b/modules/svg/include/SkSVGNode.h
index 36b27ee..c3d7d4e 100644
--- a/modules/svg/include/SkSVGNode.h
+++ b/modules/svg/include/SkSVGNode.h
@@ -29,6 +29,7 @@
     kFeComposite,
     kFeFlood,
     kFeGaussianBlur,
+    kFeOffset,
     kFeTurbulence,
     kFilter,
     kG,