Typo in vector2d initialization

Hello,

I was reading your [blog post](https://blog.adamchalmers.com/grids-1/) and I think I found a mistake here.

https://github.com/adamchalmers/const_generic_grid/blob/3fada1b906d6f39965d1ed4cb339827cdd8caebc/src/vec2d.rs#L16

When you initialize the first vector with a for-loop, I think you meant to create lines of size `width`, and not `width * height`.

Otherwise thank you for the article, it is well written and useful for rust learners like me!