Make loadshed a pie chart of the node

[noahrhodes]

Load shed shows at orange in the plot_network_status() function. This does not show the amount of load shed. Find a way to represent the percentage of load shed.

[noahrhodes]

The VegaLite pie chart (arc) type might be able to do this. Another use is generator operating point relative to capacity

https://github.com/vega/vega-lite/issues/6800

(requires vegalite.jl to support 4.9)

[noahrhodes]

code example, might need a rework to enable this. How could this be a setting??

@vlplot(
    width=400,
    height=400,
)+
@vlplot(
    data={
        values=[
        {category="Load Demand", value=.8, x=1, y=1, order=1},
        {category="Load Served", value=.2, x=1, y=1, order=2},
        {category="Load Demand", value=.6, x=2, y=2, order=3},
        {category="Load Served", value=.4, x=2, y=2, order=4},
        ]
    },
    mark="arc",
    encoding={
        theta= {field="value", type="quantitative", scale={domain= [0, 1]}},
        color= {field="category", type="nominal"},
        x={field="x", type="nominal"},
        y={field="y", type="nominal"},
        radius={value=100}
    },
    color= {
        field= "category",
      },
    order= {field="order"}
)