error importing face_alignment

Hello @1adrianb,
I was trying to import the package and not sure why this is happening. I think is from the scikit-image side but then there might be a version requirement to set to make it still work

```
import face_alignment
lib/python3.8/site-packages/face_alignment/__init__.py:7: in
from .api import FaceAlignment, LandmarksType, NetworkSize
lib/python3.8/site-packages/face_alignment/api.py:4: in
from skimage import io
lib/python3.8/site-packages/skimage/__init__.py:135: in
from .data import data_dir
lib/python3.8/site-packages/skimage/data/__init__.py:64: in
from pooch.utils import file_hash
E ImportError: cannot import name 'file_hash' from 'pooch.utils' (/lib/python3.8/site-packages/pooch/utils.py)
```

The error occurs when importing face_alignment due to a missing 'file_hash' import from pooch.utils. Check the dependencies in setup.py or requirements.txt, particularly the versions of scikit-image and pooch. Look at the import chain in face_alignment/api.py and skimage/__init__.py to see which version of pooch is compatible. Test by installing a specific version of pooch that provides file_hash.

索引モデルが issue の本文から書いたものです。