Resize doesn't work with `horizontal: true`

I'm not sure if this is intentional - maybe it's just that I don't fully grasp what this setting means, but I can't imagine a scenario where the container width shouldn't accommodate upon resize; and that's what I see when I set `horizontal` to `true`.

I checked the official CodePen `horizontal` example, and I see the same result, it's not resizable. The grid gets a width value on page load, and this value doesn't get updated when the viewport is resized.

**Test case:** https://codepen.io/desandro/pen/naPxde

Thanks for taking a look into this.

Start with the linked CodePen horizontal example and reproduce the issue by resizing the viewport after the grid loads. Trace how the horizontal setting determines the grid width and how resize handling is triggered; done means the container width updates when the viewport is resized.

Written by the indexing model from the issue text.