Migrate metadata to static pyproject.toml

[astrojuanlu]

Observed a weird CI failure on a project using import-linter coming from pip trying to build a wheel, and even though it was not import-linter's fault, I went ahead and migrated the project metadata to static pyproject.toml, the modern replacement for setup.py.

No change in build backend was made (it was using setuptools before, and it's still using setuptools). Notice that pip install build && python -m build will produce both a sdist and a binary wheel, that you can then upload to PyPI.

I compared the resulting wheel, before and after this PR, and these are the only differences:

--- dist.old/import_linter-1.8.0.dist-info/METADATA     2023-04-17 19:09:56
+++ dist.new/import_linter-1.8.0.dist-info/METADATA     2023-04-17 19:33:36
@@ -2,11 +2,10 @@
 Name: import-linter
 Version: 1.8.0
 Summary: Enforces rules for the imports within and between Python packages.
-Author: David Seddon
-Author-email: david@seddonym.me
+Author-email: David Seddon <david@seddonym.me>
 License: BSD 2-Clause License
 Project-URL: Documentation, https://import-linter.readthedocs.io/
-Project-URL: Source code, https://github.com/seddonym/import-linter/
+Project-URL: Source-code, https://github.com/seddonym/import-linter/
 Classifier: Development Status :: 5 - Production/Stable
 Classifier: Intended Audience :: Developers
 Classifier: License :: OSI Approved :: BSD License

[seddonym]

Thanks for this and sorry for the delay in acknowledging.

There's another recent issue asking for wheels too. #166. I am pretty sure I will start doing it, it's just new to me and I want to make sure I understand the implications first.