text: Title: [FEA] Line graph transform and enrichments
  Body: **Is your feature request related to a problem? Please describe.**
  Graph compute libraries like `cuGraph` support all sorts of node-centric community detectors, but generally not edge-centric ones, which are needed for SNA. The line graph transform, esp. GPU-accelerated, would simplify reusing node-centric classifiers for edges, especially if paired with reverse projection method.
  
  **Describe the solution you'd like**
  
  1. Methods `to_line_graph`, `from_line_graph`, and maybe `enrich_from_g`
  
  ```python
  g = graphistry.edges(...)
  lg = g.to_line_graph()
  lg2 = ... cuGraph.communtity ...
  g2 = lg2.from_line_graph()
  g2b = g.enrich_from_g(node_attribs=[..], edge_attribs=[...])
  ```
  
  2. Docs example featuring community detection on edges:
  - transform
  - edge community
  - reverse transform
  - propagation to node multi-label community classification
  
  **Describe alternatives you've considered**
  - Explicit line graph type: doesn't seem necessary
  - more generic `from_line_graph`: doesn't seem necessary
  
  **Additional context**
  
  The prime motivator is really for community detection algs, but worth checking if others
  