Added another missing icon

Summary: Just commiting another icon added by the script

Reviewed By: jknoxville

Differential Revision: D19578661

fbshipit-source-id: 9da953cec30d6ac1ea68312c060a8ce4c298fac0

static/icons.json

@@ -349,5 +349,8 @@
   ],
   "send-outline": [
     16
+  ],
+  "paper-stack": [
+    12
   ]
-}
+}