render Pluto notebooks nicely

[williamstein]

Here is an example Pluto.jl Julia notebook that was published:

https://cocalc.com/share/public_paths/9ebc757b6713a9e7a41463992819c679ac63916a

This discussion

https://github.com/fonsp/Pluto.jl/discussions/1149

suggests there is a way to convert a Pluto.jl notebook to html.

We could use that to render such notebooks in a way that looks better than raw text.

[williamstein]

This is very relevant: https://github.com/JuliaPluto/PlutoSliderServer.jl