Support python 3.12

[andersonhc]

Add python 3.12 on the CI

Checklist:

• The GitHub pipeline is OK (green),
  meaning that both pylint (static code analyzer) and black (code formatter) are happy with the changes of this PR.

• A unit test is covering the code added / modified by this PR

• This PR is ready to be merged

• In case of a new feature, docstrings have been added, with also some documentation in the docs/ folder

• A mention of the change is present in CHANGELOG.md

By submitting this pull request, I confirm that my contribution is made under the terms of the GNU LGPL 3.0 license.

[andersonhc]

JPype is failing on python 3.12 and they already have an issue reporting this:
jpype-project/jpype#1147

[Lucas-C]

Hi @andersonhc

Was it intentional to merge this PR, while the GitHub Actions pipeline was still failing?

I'm not sure if this is related, but the last pipeline execution on master following this merge is failing: https:/py-pdf/fpdf2/actions/runs/7096327931

[Lucas-C]

I think the problem only occurs under Python 3.7 that installs fonttools==4.38.0, which is an older version of fonttools: https://pypi.org/project/fonttools/#history

The problem is that when you merged this PR on this repository master branch, you restored Python 3.7 in our GitHub Actions matrix: a0bf1cd

A rebase should probably have been performed before merging.
I'm going to fix this now.

[Lucas-C]

Fixed in c4da2ef

[andersonhc]

Thank you for fixing it @Lucas-C,
I messed up resolving conflict after the rebase and didn't notice