src/tox.ini: Add cython-lint

[mkoeppe]

📚 Description

Adding the command sage --tox -e cython-lint.
See https://pypi.org/project/cython-lint/

There are many failures, so it is not run by default.

📝 Checklist

• The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

[fchapoton]

ERROR: /__w/sage/sage/src/tox.ini:200: duplicate name 'description'

[fchapoton]

and the doc does not build

[mkoeppe]

@fchapoton chapoton Should we also add a "cython-lint-minimal" that would be run automatically?

[fchapoton]

There is no urgency. I see no way among the command-line options to select a subset of checks. It seems that one can only ignore some checks.

[fchapoton]

ok

[mkoeppe]

Thanks!