Blacksheep-sqlalchemy

- Upgrade versions of dependencies.
- Handle setuptools warning: _SetuptoolsDeprecationWarning: License classifiers are deprecated_.
- Add Python 3.13 to the build matrix, remove Python 3.8.

- Upgrades the library to use `pyproject.toml`.
- Updates the GitHub Workflow.
- Updates the LICENSE contact.

- Unpins the `SQLAlchemy` version from requirements

- First working implementation, with integration offering injection of
db connections and ORM sessions provided by SQLAlchemy