UV of Float32x3 causes GPU buffer issue in 0.6.0 (works fine in 0.5.0)

## Bevy version

Release 0.6.0

## Operating system & version

Tested: Windows 10, MacOS 12.1

## What you did
Follow duplication steps in https://github.com/WAFFO/bevy_0.6.0_mesh_issue

I originally ran into this issue migrating my project and encountered a computer killing monster where my heightmap mesh once was. (Pictured below)

This was OS breaking, and I had to hold my power button to escape.

## What you expected to happen

To draw a flat square made of two triangles, 4 vertices. (Pictured: 0.5.0)

## What actually happened

One triangle, standing. (Pictured: Same mesh code in 0.6.0)

## Additional information

If the mesh is really big (like for a heightmap) my computer comes to a halt and I have to hold the power button to reset. I suspect something is not aligned in the GPU buffer.


# The Culprit!

It's this line here: https://github.com/WAFFO/bevy_0.6.0_mesh_issue/blob/v6/src/main.rs#L83
```rust
let uvs = vec![[0.0, 0.0, 0.0]; vertices.len()];
```
Change it from a `[f32; 3]` to a `[f32; 2]`
```rust
let uvs = vec![[0.0, 0.0]; vertices.len()];
```
And now it works perfectly!

# This shouldn't be allowed to happen :(
It took a long time for me to figure out why my mesh was breaking in 0.6.0.

Since it worked in 0.5.0, I have to ask if it's intended for `[f32; 3]` to not work for the UV attribute. If so, a type check or some error is needed. Otherwise, it's a bug!