Multiplot: improve API and add documentation to the website #4345
Description
A MVP Multiplot was recently added #4344
Its API should be improved to use more logical types, and also allow users to add Plots up front and arrange them later according to a specified number of rows and columns.
Plot plot1 = new();
var sig1 = plot1.Add.Signal(Generate.Sin());
sig1.Color = Colors.Blue;
sig1.LineWidth = 5;
Plot plot2 = new();
var sig2 = plot2.Add.Signal(Generate.Cos());
sig2.Color = Colors.Red;
sig2.LineWidth = 5;
MultiPlot mp = new();
mp.AddSubplot(plot1, 0, 2, 0, 1);
mp.AddSubplot(plot2, 1, 2, 0, 1);
mp.SavePng("test.png");