FAQ: How to create a custom plottable (plot type)

[swharden]

Add a FAQ page demonstrating how to create a custom plot type (idea from ScottPlot/ScottPlot#1999)

Basic Steps to Create a Custom Plot Type

• Create a CustomPlottable class that implements IPlottable
• Instantiate your plottable: CustomPlottable myThing = new()
• Add it to your plot formsPlot1.Plot.Add(myThing)