Blacksheep-cli

- Add the `--checkout` option to the `create` command to support using specific
branches and tags. Example:
`blacksheep create my-proj2 --template mvc --checkout v1.0.2`.
- Add support for `int` and `float` question types.
- Add missing `__init__.py` files.
- Update dependencies, apply latest formatting from `black`.
- Workflow maintenance.
- Remove Python 3.8 from the build matrix, add Python 3.12 and 3.13.

- Add support for Git repositories cloned over SSH.
- Add support for Cookiecutter [directories](https://cookiecutter.readthedocs.io/en/stable/cli_options.html#cmdoption-cookiecutter-directory).

- Add support for conditional questions.

- Correct error when stopping a template questionary.

- First working release.