feat: add PEP 561 compliance (typing in installed package)

[ArturLange]

Description

Right now for packages which use openfoodfacts python package mypy complains about missing typing:

app/tasks.py:4: error: Skipping analyzing "openfoodfacts": module is installed, but missing library stubs or py.typed marker  [import-untyped]

Solution

In order for typing to work we need to mark package with py.typed file to comply with PEP 561 and let mypy and other tools know that typing should work with that package.
See https://mypy.readthedocs.io/en/stable/installed_packages.html#using-installed-packages-with-mypy-pep-561

[sonarcloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
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See analysis details on SonarCloud

[alexgarel]

Thanks @ArturLange !