[skotty] Add Json DM source

Generates a filmstrip with evenly distributed frames for a Skotty animation.

TBR=
Change-Id: Ia89e0d65d59fd5ab4ef221a231e9b3e0c033828a
Reviewed-on: https://skia-review.googlesource.com/90025
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index a61bff7..8344b54 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1503,6 +1503,7 @@
       include_dirs = [ "tests" ]
       deps = [
         ":common_flags",
+        ":experimental_skotty",
         ":experimental_sksg",
         ":experimental_svg_model",
         ":flags",