Add mypy.ini

[mkoeppe]

Configuration from #36198 (comment) @fchapoton @jhpalmieri

📝 Checklist

• The title is concise and informative.
• 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

[github-actions]

Documentation preview for this PR (built with commit 8b81855; changes) is ready! 🎉

[jhpalmieri]

Do we need to specify python_version?

[mkoeppe]

No idea, I don't use this tool

[jhpalmieri]

Frédéric, comments?

[fchapoton]

• This may be slightly prematurate, as typing annotations are very sparse currently in sage, and nowhere ready for full automatic check.

• I think one should maybe put here the oldest python version that sage currently supports.

[mkoeppe]

• This may be slightly prematurate, as typing annotations are very sparse currently in sage, and nowhere ready for full automatic check.

Well, adding the ini file does not set it up to be checked automatically.

[fchapoton]

ok, well

[mkoeppe]

Thanks