Introduce render?

[ajkeller34]

It would be nice to be able to use render methods without introducing a cell, just to get the raw polygons. Perhaps something like

r = Rectangle(10µm, 10µm)
plgs = render(r, Rectangles.Rounded(2µm))

[ajkeller34]

On a related note, there could be a render! method that acts on an array of polygons instead of a cell, e.g.

r = Rectangle(10µm, 10µm)
plgs = render(r, Rectangles.Rounded(2µm))
render!(plgs, r + Point(20µm, 20µm), Rectangles.Plain())