Curate N MNIST task

[JesusEV]

Add curated script

• [x] fix mypy, pylint, flake8 errors, see: https://github.com/JesusEV/nest-simulator/actions/runs/8391688951/job/22982620710
• [ ] Add new image

[akorgor]

Please fix pylint, flake8, black errors.

[JesusEV]

@akorgor It seems to me that the MNIST classification task does not contribute much to this tutorial. The N-MNIST task provides everything that the MNIST could provide and more

[akorgor]

@akorgor It seems to me that the MNIST classification task does not contribute much to this tutorial. The N-MNIST task provides everything that the MNIST could provide and more

I agree!