chore: add ffmpeg dist zip (#14681)

BUILD.gn

@@ -906,6 +906,15 @@ dist_zip("electron_dist_zip") {
   ]
 }
 
+dist_zip("electron_ffmpeg_zip") {
+  data_deps = [
+    "//third_party/ffmpeg",
+  ]
+  outputs = [
+    "$root_build_dir/ffmpeg.zip",
+  ]
+}
+
 group("electron") {
   deps = [
     ":electron_app",