run python 3.12 in the build, formatting tweaks

[fuhrysteve]

No description provided.

[Mikaayenson]

👋 @fuhrysteve Do you think we can get this PR in? IINM It addresses #182 .

[vladyslav2]

@fuhrysteve Please!

[matejsp]

We are currently blocked because of this project. Any change to release this PR ?

[JC3]

I don't know what's going on with this PR but if anybody needs to use it, I've released this branch on PyPi as marshmallow-jsonschema-python3. It's just the py3.12 branch.

Note the version number is 0.13.1 (not 0.13.0), because I messed up, heh.

So you can replace marshmallow-jsonschema with marshmallow-jsonschema-python3 to get a version that works on Python 3.12. Be sure to pip uninstall any existing marshmallow-jsonschema first.

[matejsp]

Alternative is to migrate to apispec with marshmallow plugin:
https://apispec.readthedocs.io/en/latest/using_plugins.html

We have done so and couldn't be more happy.