Document how to display a plot with Mux.jl

I've read through the tutorial, but am struggling to get a plot to display in my browser. I run Julia on a remote server, so I'd like it to be served via an HTTP server. The documentation for PlotlyJS.jl mentions that this should be easy to do with WebIO and Mux, but doesn't say how.

From googling, it looks like I should use the `webio_serve` function, but the function doesn't have any documentation and its signature doesn't specify the argument type. How do I take a Plot or SyncPlot and wrap it in something that Mux can serve?