add comments to core.js about order of registering components

Author: archmoj

src/core.js

@@ -44,8 +44,8 @@ register([
     require('./components/errorbars'),
     require('./components/colorscale'),
     require('./components/colorbar'),
-    require('./components/legend'),
-    require('./components/fx'), // fx needs to come after legend
+    require('./components/legend'), // legend needs to come after shape | legend defaults depends on shapes
+    require('./components/fx'), // fx needs to come after legend | unified hover defaults depends on legends
     require('./components/modebar')
 ]);