add a plotting function for networks using NetworkX

[LegrandNico]

The plot_network function is currently using GraphViz, however, it would be convenient to have something more Matplotlib-compatible, and NetworkX seems to be the go-to library. This would also let us convert our networks into this format, which can provide many metrics tools, and can be further exported to PyVis, which could be nice also to support.

The first step would be to convert the plot_network function into a NetworkX equivalent.