Optimize gitignores

Summary:
Use `tools/scm/optimize-gitignore.py` to optimize gitignores in fbcode,
fbandroid, and fbobjc, by moving rules to subdirectories.

Reviewed By: phillco

Differential Revision: D9660076

fbshipit-source-id: 3321ebaafb93e387a11fab000ba9e80afc88b210

Libraries/Animated/release/.gitignore

@@ -0,0 +1,3 @@
+/lib/
+/dist/
+/node_modules/