## Objective
The `MotionBlur` component exposes renderer internals. Users shouldn't
have to deal with this.
```rust
MotionBlur {
shutter_angle: 1.0,
samples: 2,
#[cfg(all(feature = "webgl2", target_arch = "wasm32", not(feature = "webgpu")))]
_webgl2_padding: Default::default(),
},
```
## Solution
The renderer now uses a separate `MotionBlurUniform` struct for its
internals. `MotionBlur` no longer needs padding.
I was a bit unsure about the name `MotionBlurUniform`. Other modules use
a mix of `Uniform` and `Uniforms`.
## Testing
```
cargo run --example motion_blur
```
Tested on Win10/Nvidia across Vulkan, WebGL/Chrome, WebGPU/Chrome.
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