Feature suggestion: phylogenetic outlines

[taprs]

Dear Klaus,

Thank you for your wonderful work!

I was wondering if you would find it useful to implement phylogenetic outlines on NeighborNet split sets as described here and showcased here (the relevant part is outline_algo.py). I think getting an outline = the same network object with fewer edges could be an option for as.networx.splits() for a start.

Having less edges helps a lot when visualizing large networks, and I would love to integrate outlines into my existing workflow in phangorn without having to rely on the unsupported and imperfect Python library.

Best regards,
Nikita