Sunset Python 3.7 support and clarify supported versions

[banesullivan]

According to PEP 537, Python 3.7 has stopped maintenance in June 2023. NumPy's NEP 29 dropped Python 3.7 in 2021. So it's time to drop it here too, and replace it with Python 3.11 where used on CI:

https://github.com/raphaelquast/EOmaps/blob/71361494f5af1fb6674c9862339d0e40946f5e89/.github/workflows/Publish_to_PyPi.yml#L19

Please also reference a request from @jhkennedy in https://github.com/pyOpenSci/software-submission/issues/138#issuecomment-1858583110:

It's not clear what python versions EOMaps supports:

• There's no badge on the README, or in the PyPI metadata about supported versions
• python_requires is not set in setup.py
• classifiers in the setup.py only list Python 3.7, but I see that EOMaps is only tested on Python 3.8-3.10
• The conda-forge recipe supports Python >=3.6, so users can install into Python 3.11 and 3.12, but it's not being tested on those versions

I'd really like to see this cleaned up, with the supported python versions clearly listed, and all supported versions tested.

*Note: I also have some additional comments related to this when setting up a development environment.

[raphaelquast]

The pending PR for EOmaps v8.0 (#205) now includes the following changes:

• minimal python version is explicitly stated in pyproject.toml as >3.8
• unittests run on 3.8 - 3.11
  • support for python 3.12 is currently waiting for the 3.12 support PR from numba (required by datashader) which is about to be merged soon
• conda-forge recipe will be updated accordingly once EOmaps v8.0 is released

[banesullivan]

Great work!