Generate .pyi stubs

The idea is to use https://github.com/Jij-Inc/pyo3-stub-gen

However it depends on the following pull requests
- https://github.com/PyO3/rust-numpy/pull/435 (and its integration into pyo3-stub-gen)
- https://github.com/Jij-Inc/pyo3-stub-gen/pull/84
- https://github.com/Jij-Inc/pyo3-stub-gen/issues/82