Support compiling bevy_rapier on bevy_ecs without the rest of bevy

[FeldrinH]

Would it be possible to support compiling and running this library with only bevy_ecs (https://crates.io/crates/bevy_ecs) as dependency, instead of the whole bevy engine, or are there some festures from other bevy components which the crate requires?

[dman-os]

Just from a quick glance, it makes use of bevy_app(plugins and events), bevy_transform and bevy_render and I don't see anything that can't be put behind feature gates.