Examples: Added helpers to light probe examples

[WestLangley]

Added the light probe helpers to the light probe examples.

It is important to verify that:

(1) the irradiance inferred from the environment map is correct,

(2) the computed SH3 coefficients are correct, and

(3) the helper renders correctly.

Also added a notation that the light probes position property, which is important in a light probe volume, is only honored when rendering the helper. The light probe position is currently not used in the lighting calculations.

[WestLangley]

How did the screen shots pass without updating them?

Also, webgl_lightprobe_cubecamera.html seems to be redundant given webgl_lightprobe.html.

[Mugen87]

Also, webgl_lightprobe_cubecamera.html seems to be redundant given webgl_lightprobe.html.

webgl_lightprobe_cubecamera covers a different use case since it generates the light probe from a render target. This code path is not yet supported in WebGPURenderer.

[Mugen87]

How did the screen shots pass without updating them?

That is indeed strange. I suggest to still regenerate the screenshot to avoid fails in future CI runs.

[WestLangley]

@Mugen87 webgpu screenshots render black for me. Is there a secret?

[Mugen87]

Have you lately executed a npm i? Maybe the dev dependencies are outdated...

[WestLangley]

I'm using homebrew... In the mean time, can you please update the webgpu screen shot?