text: Title: Display a dropdown in the filter UI for categorical filtering
  Body: Hi,
  
  I'm new to plotly dash and I've googled but I don't see a way to make a filter a dropdown akin to excel filters.
  
  I've seen people do "hacks" but this should be the default behaviour out of the box (or at least a setting).
  
  I'm currently evaluating plotly dash vs tools such as metabase and metabase has this out of the box.
  
  From a UX pov, filters with a dropdown is a huge win and important for users.  when looking at a new dataset, the filters hint + tell the user what values are in the column.  Freeform text doesn't tell this story to the user.