Add basic permissively licensed rigged humanoid asset

## What problem does this solve or what need does it fill?

Humanoid models are both very useful for testing new animation features, and great for more complex and realistic examples.

However, Bevy's repo doesn't currently have one!

## What solution would you like?

Build and upload a humanoid model with the following specs:

- moderately low polygon count to reduce repo bloat
- modest number of bones, with a standard rigging
- at least one basic skeletal animation to start
- aesthetically competent
- good proportions
- realistic proportions
- permissively licensed: CC0 or CC-BY, CC-BY-SA at most
- in gltf format

## What alternative(s) have you considered?

Use an existing standard, like [this third person character controller](https://assetstore.unity.com/packages/essentials/starter-assets-third-person-character-controller-urp-196526) or a [Mixamo](https://www.mixamo.com/#/?page=1&type=Character) character. Unfortunately, these are not permissively licensed!

We could also examine [Kenney's characters](https://kenney.nl/assets/animated-characters-2), and either adapt them to meet our needs or use them directly.

Review the requested humanoid asset specifications and compare the referenced Kenney, Mixamo, and Unity options, including their licenses. Produce a moderately low-poly, realistically proportioned rigged humanoid with a modest standard skeleton, at least one basic animation, and a permissive license, then export it in glTF format.

Written by the indexing model from the issue text.