Examples: Add Compute Reduction Example

[cmhhelgeson]

Adds an example demonstrating some very simple GPGPU reduction algorithms, with the intention to add more as time goes on. I'd love to take any suggestions for demonstrating reduction in a more visually appealing way beyond the standard buffer grid approach that's been used in webgpu_compute_sort_bitonic and webgpu_storage_buffer.

[WestLangley]

Ephemeral test link
https://raw.githack.com/cmhhelgeson/three.js/webgpu_compute_reduce/examples/webgpu_compute_reduce.html