## Objective
- Remove the second to last `bevy_animation` dependency on
`bevy_render`.
- Update some older documentation to reflect later changes to the crate.
## Narrative
I'm trying to make `bevy_animation` independent of `bevy_render`. The
documentation for `bevy_animation::AnimatableProperty` is one of the
last few dependencies. It uses `bevy_render::Projection` to demonstrate
animating an arbitrary value, but I thought that could be easily swapped
for something else.
I then realised that the rest of the documentation was a bit out of
date. Originally `AnimatableProperty` was the only way to animate a
property and so the documentation was quite detailed. But over time the
crate has gained more documentation and other ways to hook up
properties, leaving parts of the docs stale or covered elsewhere. So
I've slimmed down the `AnimatableProperty` docs and added a link to the
main alternative (`animated_field`).
I've probably swung too far towards brevity, so I can build them back up
if preferred. Also the example is kinda contrived and doesn't show the
range of `AnimatableProperty`, like being able to choose different
components. And finally the memes might be a bit stale?
## Showcase
## Testing
```
cargo doc -p bevy_animation --no-deps --all-features
cargo test -p bevy_animation --doc --all-features
```
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