A raycasting backend for `bevy_mod_picking` that uses `rapier` for raycasting.
# Usage
If a pointer passes through this camera's render target, it will
automatically shoot rays into the rapier scene and will be able to pick things.
To ignore an entity, you can add [`Pickable::IGNORE`] to it, and it will be ignored during
raycasting.
For fine-grained control, see the [`RapierBackendSettings::require_markers`] setting.
## Limitations
Because raycasting is expensive, only the closest intersection will be reported. This means that
unlike some UI, you cannot hover multiple rapier objects with a single pointer by configuring
the [`Pickable`] component to not block lower elements but still emit events. As mentioned
above, all that is supported is completely ignoring an entity with [`Pickable::IGNORE`].
This is probably not a meaningful limitation, as the feature is usually only used in UI where
you might want a pointer to be able to pick multiple elements that are on top of each other. If
are trying to build a UI out of rapier entities, beware, I suppose.