Add Support for Triggering Events via AnimationEvents

[atornity]

Objective

Add support for events that can be triggered from animation clips.

Closes #15494

Solution

Added a new field to AnimationClip: events, which contains a list of AnimationEvents. These are automatically triggered in trigger_events.

Note that there is currently no guarantee that events will be triggered in the correct order in instances were multiple events are triggered in the same update tick.
Specifically, if the animation looped on this tick and there is one event at the start of the animation, and one event at the end of it, the event at the start will be triggered first simply because events are sorted by the time.
This could probably be accounted for somehow, not sure how though.
Fixed!

Testing

Added a couple of tests and examples to make sure events are triggered when expected.

• Did you test these changes? If so, how?
• Are there any parts that need more testing?
• How can other people (reviewers) test your changes? Is there anything specific they need to know?
• If relevant, what platforms did you test these changes on, and are there any important ones you can't test?

---

Showcase

animation events can be added by specifying a time and event.

animation_clip.add_event(1.0, SomeEvent);

and optionally, providing a target id.

let id = AnimationTargetId::from_iter(["shoulder", "arm", "hand"]);
animation_clip.add_event_to_target(id, 1.0, HandEvent);

Added two new animation examples, animation_events and bunny_detective.

The model is my own and it's CC0: https://opengameart.org/content/detective-bunny

[github-actions]

The generated examples/README.md is out of sync with the example metadata in Cargo.toml or the example readme template. Please run cargo run -p build-templated-pages -- update examples to update it, and commit the file change.

[github-actions]

The generated examples/README.md is out of sync with the example metadata in Cargo.toml or the example readme template. Please run cargo run -p build-templated-pages -- update examples to update it, and commit the file change.