Support subword and word language models

Closes #199 (closed)

Ref https://redmine.teklia.com/issues/4941

dan/datasets/entities/__init__.py

+# -*- coding: utf-8 -*-
+"""
+Extract entities from Arkindex using a corpus export.
+"""
+from pathlib import Path
+
+from dan.datasets.entities.extract import run
+
+
+def add_entities_parser(subcommands) -> None:
+    parser = subcommands.add_parser(
+        "entities",
+        description=__doc__,
+        help=__doc__,
+    )
+    parser.add_argument(
+        "database",
+        type=Path,
+        help="Path where the data were exported from Arkindex.",
+    )
+    parser.add_argument(
+        "--output-file",
+        type=Path,
+        default=Path("entities.yml"),
+        required=False,
+        help="Path to a YAML file to save the extracted entities.",
+    )
+    parser.set_defaults(func=run)