Use Penrose to visualize e-graphs

[adamslc]

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This is a speculative issue. It would be great to visualize an e-graph, and in particular how the saturation proceeds. Arranging the diagram in a visually informative way seems in principle quite difficult. However, Penrose supposedly solves this problem by optimizing diagrams.

[0x0f0f0f]

Interesting idea. There's also #41 Something based on https://juliagraphs.org/GraphPlot.jl/ might also be cool to do, but I guess a native GraphViz approach may be the best. See how egg plots e-graphs

[0x0f0f0f]

We now have a working visualization tool with GraphViz in src/extras