Add initial skeleton nqm.irimager C extension module

[aloisklink]

Add an initial skeleton code that creates a CPython C extension module that can do:

from nqm.irimager import IRImager

irimager = IRImager()
assert irimager.test() == 42

In the future, this Python module will take care of interfacing with the MICRO-EPSILON thermoIMAGER TIM M-1 thermal camera using the libirimager C++ library.

Implementation details

Building

In order to compile this C extension module, we can use the class setuptools.Extension, which is part of setuptools.

Although this isn't officially supported by Poetry, Poetry does have a tool.poetry.build.script setting that you can enable in order to use a custom build.py script, see:

• Stabilize 'build.py' python-poetry/poetry#2740
• Add PEP517 check suite and support disabling setup.py for sdists python-poetry/poetry-core#26

This lets us modify the setuptools kwargs, so that Poetry builds our extension when doing poetry build, poetry install, or even pip3 install ..

Python C API

The official Python C API is very very C, so it's a bit wordy. IMO, it's pretty unreadable, and extremely difficult to use/write code. I've already got a future PR where I replace the official Python C API with pybind11, which is a C++ API that is muuuuuuuuuuuuuuch easier to use, so feel free to skim this bit, instead of doing a proper review. I've mainly kept the C stuff in since:

• I know @mereacre loves C code 😄
• pybind11 is quite a bit larger and slower than just using the Python C API. I think the ease-of-developer use means that we should stick with pybind11, but having the Python C API code in our git log means that we can always go back to the Python C API if we really need to eek out some more performance.

PEP 484 stubs

Python PEP 484 type hints can't be added to a C extension module, so I've instead created a stub-file for the type hints, see src/nqm/irimager/__init__.pyi.

I've initially created these stubs using poetry run stubgen -m nqm.irimager, which is the stubgen tool that is part of mypy.

In order to ensure that the stubs remain in sync, I've made a CI action that runs MYPYPATH=src poetry run stubtest nqm.irimager, which runs the stubtest tool that is part of mypy.

[AshleySetter]

Looks good to me.

Using pybind11 for brevity of code and ease of development sounds a good idea to me.

Premature optimisation is the root of all evil after all 😄

[aloisklink]

Premature optimisation

Except for optimising readability/ease-of-use. IMO, the more I look at 2-3 year old spaghetti code, the more I realize how important it is (especially when git blame says that Alois Klink wrote the code 🤦).