reflect new feature type for date in datacard (#2)

- reflect new feature type for date in datacard (31b8ca8c145480efa6701cc2edf0be37d185cd32)

README.md

@@ -88,7 +88,7 @@ The dataset contains the following fields:
 
 - `id`: Unique identifier("string"),
 - `text`: ext in the document("string"),
-- `date`: Date of publication("string"),
+- `date`: Date of publication("date64"),
 - `genre`: Broad classification("string"),
 - `head`: Often same as title. Can be missing("string"),
 - `title`: Title of document("string")