Feature request: layouts for weighted graphs

[vandenman]

If one has a weighted graph, would it make sense for the layout algorithm to account for the weights?

This is done in, for instance, the R package qgraph.

Perhaps I'm viewing this too simplistically, but I think that all that needs to be done is multiply by the weights at some point. For example, in the Spring layout, there is now

https://github.com/JuliaGraphs/NetworkLayout.jl/blob/6574223d3c915c82695761a7c1318779f498f155/src/spring.jl#L95-L102

where, if I understand the code correctly, this line F_d = d / K - K^2 / d^2 could be changed to account for the weight of the edge. One option is to simply weigh the attraction by the (normalized) edge strength, which is I think what qgraph does (see https://github.com/cran/qgraph/blob/57d588ee05a554f9d1078914e05ce03662c610b2/src/layout_rcpp.cpp#L111).

Any thoughts? I'd be happy to open a draft PR for a single layout (e.g., spring).