Create a primitive sampling showcase example (#13519)

# Objective

- Show + Visually Test that 3D primitive sampling works
- Make an example that looks nice.

## Solution

- Added a `sampling_primitives` examples which shows all the 3D
primitives being sampled, with a firefly aesthetic.


![image](https://github.com/bevyengine/bevy/assets/27301845/f882438b-2c72-48b1-a6e9-162a80c4273e)

## Testing

- `cargo run --example sampling_primitives`
- Haven't tested WASM.

## Changelog

### Added
- Added a new example, `sampling_primitives`, to showcase all the 3D
sampleable primitives.

## Additional notes:

This example borrowed a bunch of code from the other sampling example,
by @mweatherley.

In future updates this example should be updated with new 3D primitives
as they become sampleable.

---------

Co-authored-by: Alice Cecile <[email protected]>
Co-authored-by: Joona Aalto <[email protected]>

Cargo.toml

@@ -2970,6 +2970,18 @@ description = "Shows off rendering for all math primitives as both Meshes and Gi
 category = "Math"
 wasm = true
 
+# Math
+[[example]]
+name = "sampling_primitives"
+path = "examples/math/sampling_primitives.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.sampling_primitives]
+name = "Sampling Primitives"
+description = "Demonstrates all the primitives which can be sampled."
+category = "Math"
+wasm = true
+
 [[example]]
 name = "random_sampling"
 path = "examples/math/random_sampling.rs"

examples/README.md

@@ -322,6 +322,7 @@ Example | Description
 --- | ---
 [Random Sampling](../examples/math/random_sampling.rs) | Demonstrates how to sample random points from mathematical primitives
 [Rendering Primitives](../examples/math/render_primitives.rs) | Shows off rendering for all math primitives as both Meshes and Gizmos
+[Sampling Primitives](../examples/math/sampling_primitives.rs) | Demonstrates all the primitives which can be sampled.
 
 ## Reflection