Add an example for stochastic texture sampling

[cBournhonesque]

Objective

This PR adds an example that showcases how a custom material can be used to repeat a texture stochastically while avoiding repetition artifacts.
It is related to #13682.

It doesn't provide a seamless solution for users but at least it can provide an example.

I don't think it's the best implementation out there (it's my first time writing a shader and I mostly glued external code) but it seems to be working!

StochasticSampling.mov

[github-actions]

The generated examples/README.md is out of sync with the example metadata in Cargo.toml or the example readme template. Please run cargo run -p build-templated-pages -- update examples to update it, and commit the file change.

[IceSentry]

I personally don't like that kind of example because it doesn't really show any bevy api that isn't already documented in another example. I think for an example like that to be included it would need to show something that requires a lot of complexe use of bevy apis, but this just shows a simple use of the mesh and material api. Most of the complexity is in the shader. If people want it despite that I won't push back more, but I just wanted to voice this.

[cBournhonesque]

I personally don't like that kind of example because it doesn't really show any bevy api that isn't already documented in another example. I think for an example like that to be included it would need to show something that requires a lot of complexe use of bevy apis, but this just shows a simple use of the mesh and material api. Most of the complexity is in the shader. If people want it despite that I won't push back more, but I just wanted to voice this.

I think I agree. Would we want to support this kind of behaviour in-tree or let external crates provide this kind of stuff?