Doubt

Changed
- Updated `tables` dependency to v3.9.x, which fixes issues with installation of the
package. This requires Python 3.9 or above, however, so we require that here as well.

Added
- The `Boot` class now has `save` and `load` methods, which uses `joblib` under the
hood.

Changed
- The dataset-specific dependencies are now put in a separate `datasets` extra, to make
the core package more lean. You can install the package with all the dependencies
using `pip install doubt[datasets]`.

Changed
- Now also allows `pandas` 2.x.x versions.

Security
- Updated `urllib3` to 2.0.7 due to a security update.

Added
- Now saves the models during training with a `Boot` and reuses those during inference,
speeding up inference. Thanks to andrepugni for this contribution!

Fixed
- Downgraded `tables` to 3.7.x to fix an installation bug.
- Downgraded `scikit-learn` to >=1.1,<1.3, as the decision tree API in v1.3 is
incompatible with the previous ones. This will be dealt with separately in the
future.