Add default values for entity separators

Closes #194 (closed)

dan/datasets/extract/__init__.py

@@ -112,6 +112,7 @@ def add_extract_parser(subcommands) -> None:
             Do not give any arguments to keep the whole text.
         """,
         required=False,
+        default=list(map(validate_char, ("\n", " "))),
     )
     parser.add_argument(
         "--tokens",