An area() is a rectangular block of grid cells (1-based, inclusive) that a
sub-plot occupies. Pass a list of area()s (one per plot, in order) as
concat(..., design = ) to place plots on an explicit, possibly spanning,
grid.
Examples
a <- vplot(mtcars) |> mark_point(x = wt, y = mpg)
b <- vplot(mtcars) |> mark_point(x = hp, y = mpg)
concat(a, b, design = list(area(1, 1, 1, 2), area(2, 1, 2, 1)))
