Fix mdformat 1.0.0 compatibility

[kdeldycke]

This PR closes: #18

Given the big changes, I couldn't help but try to update things left and right:

• Bump minimal Python to 3.10 (to align it with mdformat 1.0.0 owns requirement)
• Remove cache compatibility import for Python 3.9
• Add tests on Python 3.14
• Remove tests on Python 3.9
• Bump pytest >= 8.4.0 (first version to support Python 3.14)
• Bump CI GitHub workflow actions

Sorry if this PR feels a bit bigger in scope than simply fixing mdformat 1.0.0 compatibility. So please tell me if some changes are too aggressive in which case I'll be happy to scale down my propositions.

[kdeldycke]

OK I finished all my changes. @csala, can you trigger the CI workflows so we can see the effects?

[csala]

Hey @kdeldycke thanks for the proposal!

I agree with many of the things that you are proposing, but I would prefer not to take this huge PR in at once and rather do things one by one.

Would you mind making this PR strictly about issue #17, without any of the other unrelated changes (including #18, which I would like to treat separately)

[kdeldycke]

Yes, no worries! As in csala/mdformat-simple-breaks#4, I'll scale down the PR and make separate proposals. Thanks for the quick answer! :)

[kdeldycke]

@csala Just finish splitting up all changes into independent PRs. Also reduced the changes for each to their minimum. All are ready to be reviewed and merged upstream! :)

[kdeldycke]

Same as csala/mdformat-simple-breaks#4 , I just merged #23 on top of this one to fix the mutually dependent PRs.

@csala can you triggers the workflows on this one too?

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.29%. Comparing base (b476b07) to head (6302a30).
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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #19      +/-   ##
==========================================
+ Coverage   92.50%   97.29%   +4.79%     
==========================================
  Files           2        2              
  Lines          40       37       -3     
==========================================
- Hits           37       36       -1     
+ Misses          3        1       -2     

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[csala]

All checks passed, so merging this. Thanks @kdeldycke !

[kdeldycke]

Yeah! Happy to see everything's right! Thanks for the merge! :)