Allow Adding already-packed Rectangles to be added as-is to a packer

[Raildex]

Scenario:
I want to pack polygon Texture Coordinates.

For that I go through each polygon and return the packed rectangle's absolute pixel rectangle coordinates back to the polygon and are later transformed to UV coordinates by dividing by the dimensions of the resulting bounds later.

However, since I do not know how many rectangles I am about to pack, I can't have a "upper limit" for the bounds. For this reason, I would welcome a method to add a List<PackedRectangle> to an already existing Packer which just adds the Packed Rectangles to the packer's internal list. (if the rectangles do not fit because the bounds are too small, just throw an exception?)

This way, The Bounds can grow without invalidating previous packed rectangles.