Revise code setRowClassName for <Grid />

Revise code setRowClassName for , make sure it works properly and it is documented in StoryBook.

Start by locating the Grid entry point and the existing setRowClassName implementation, then find the related StoryBook documentation. Verify the current behavior and document the revised usage; the work is done when setRowClassName works properly and its behavior is covered in StoryBook.

索引モデルが issue の本文から書いたものです。