skfmm python 3.12 compatibility

[mdp0023]

Having an issue installing skfmm (using pip install scikit-fmm and conda install scikit-fmm) I believe is coming from a compatibility issue with python 3.12.

They've developed a fix on a separate branch (pip install git+https://github.com/scikit-fmm/scikit-fmm.git@meson) but has not been merged with the main branch yet. Will need to be checked later for compatibility.

When fixed, update requirements.txt file and github actions documentation file