Improve many_sprites example

[alice-i-cecile]

How can Bevy's documentation be improved?

Link.

Things that could be better:

1. It's unclear why we need both a Transform and Position component. Usually, Transform itself contains this information.
2. move_camera should use a query filter along with query.single to only move, well, the camera.
3. Use spawn_batch for spawning many sprites.

[willolisp]

Well, this one looks simple enough that I could give it a shot, if there's nobody else working on it.

[alice-i-cecile]

@willolisp that sounds great :) I don't think anyone else is tackling this right now so feel free!

[willolisp]

@alice-i-cecile hmmm actually, looks like #2078 already fixes this and is just waiting for a more thorough review? Should I just close my PR?

[alice-i-cecile]

@willolisp right, thanks for the reminder. Sorry for missing this; duplicating work always feels bad 😅

I slightly prefer the changes in #2785; I think it's a bit more direct in a few places (like the timer system) and doesn't rely on hard-to-explain constants for positioning. When merging, we should give credit to both you and @neosam in some fashion.