Add counts attribute to parcats_hovermode_dimension mock

Makes the hoverlabel shifting logic more noticeable and shows off
the `counts` attribute

Author: Jon M. Mease

test/image/mocks/parcats_hovermode_dimension.json

@@ -9,7 +9,8 @@
         {"label": "Two",
           "values": ["A", "A", "A", "B", "A", "A", "A", "A", "C"],
           "categoryorder": "category descending"},
-        {"label": "Three", "values": [11, 11, 11, 11, 11, 11, 11, 11, 11]}]
+        {"label": "Three", "values": [11, 11, 11, 11, 11, 11, 11, 11, 11]}],
+      "counts": [11, 3, 5, 2, 1, 20, 5, 9, 1]
     }
   ],
   "layout": {