[svg] Add SkSVGFeMerge.cpp to public.bzl

Another followup to http://review.skia.org/823896

Change-Id: I5b60b80d057bee53a67c2b511dd3fd087f60d7aa
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/852056
Commit-Queue: Florin Malita <fmalita@google.com>
Auto-Submit: Florin Malita <fmalita@google.com>
Reviewed-by: Kaylee Lubick <kjlubick@google.com>
1 file changed