This node creates curve splines from mesh edges. A selection attribute
input allows only using some of the edges from the input mesh. The node
builds cyclic splines from branchless groups of edges where possible,
but when there is a three-way intersection, the spline stops.

The algorithm is from Animation Nodes, written by @Omar Emara (OmarSquircleArt).
(find the original pull request here). I added the selection and used different variable
names, etc, but other that the algorithm is the same (in general the way AN
handles splines is fairly similar to node splines in Blender).