Wrapper over stbrectpack_sys, offering a cleaner abstraction than the bindgen generated interface.
```Rust let mut rects = vec![Rect::new(1280, 720); 4];
pack(&mut rects, 2560, 1440).unwrap();
asserteq!(rects[0].packedtopleftx, 1280); asserteq!(rects[0].packedtoplefty, 720);
asserteq!(rects[1].packedtopleftx, 0); asserteq!(rects[1].packedtoplefty, 0);
asserteq!(rects[2].packedtopleftx, 1280); asserteq!(rects[2].packedtoplefty, 0);
asserteq!(rects[3].packedtopleftx, 0); asserteq!(rects[3].packedtoplefty, 720); ```