Add path complex neural network in TopoModelX

[mhajij]

What

Implement a path complex neural network.

Why

Currently TopoModelX has networks for hypergraphs, simp, cell and combinatorial complexes. TopoNetX supports all these complexes as well as Path Complex, yet the package does not have any neural networks build for path complexes.

How

Follow the templates we have for other networks, add layer and network classes. Add a tutorial in the tutorial folder under path folder, add unit tests.