feat: add loader for open office odt files (#4405)

# ODF File Loader

Adds a data loader for handling Open Office ODT files. Requires
`unstructured>=0.6.3`.

### Testing

The following should work using the `fake.odt` example doc from the
[`unstructured` repo](https://github.com/Unstructured-IO/unstructured).

```python
from langchain.document_loaders import UnstructuredODTLoader

loader = UnstructuredODTLoader(file_path="fake.odt", mode="elements")
loader.load()

loader = UnstructuredODTLoader(file_path="fake.odt", mode="single")
loader.load()
```

tests/integration_tests/document_loaders/test_odt.py

@@ -0,0 +1,12 @@
+from pathlib import Path
+
+from langchain.document_loaders import UnstructuredODTLoader
+
+
+def test_unstructured_odt_loader() -> None:
+    """Test unstructured loader."""
+    file_path = Path(__file__).parent.parent / "examples/fake.odt"
+    loader = UnstructuredODTLoader(str(file_path))
+    docs = loader.load()
+
+    assert len(docs) == 1