Rustimport

- Fixed typo in log message (thanks miikka-oura)
- Documentation improvements for the public-facing api

* Added py.typed marker file for static type checking (thanks beauxq)

- Updated default pyo3 version to 0.21.2 and adjusted to the new `Bound<'py, T>` smart pointer in pyo3 template (thanks for reporting jermatic)

---
**PyO3 compatibility note**: Templating-dependent extensions experiencing problems with the new pyo3 version need to either [migrate their code](https://pyo3.rs/v0.21.2/migration) or fix their pyo3 version by adding a manifest comment like this at the top of their rust source file(s):

diff
// rustimport: pyo3

+ //: [dependencies]
+ //: pyo3 = { version = "0.18.3", features = ["extension-module"] }

––snip––


**Full Changelog**: https://github.com/mityax/rustimport/compare/v1.4.0...v1.5.0

- Added Jupyter/IPython support (thanks thomasjpfan)

- Fixed newly introduced bug causing deletion of the cached the target folder on rebuild (thanks mhandb)

- Fixed deleted files still being present in the demporary build dir causing compilation errors in certain cases (thanks mhandb)