`TextureAtlasSprite` has no docs

[alice-i-cecile]

How can Bevy's documentation be improved?

[TextureAtlasSprite] has no documentation, making it very hard to figure out:

1. What it is, in summary
2. How it differs from Sprite
3. How you might construct it
4. How you might use it
5. How it relates to the Handle<Image>s you might get out of a TextureAtlas

Similar changes for Sprite and even UiImage may make sense to do in the same PR.

[rparrett]

Seems like this was fixed and/or made obsolete by #5103