Document `intersects_obb`

## How can Bevy's documentation be improved?

[`intersects_obb`](https://docs.rs/bevy/latest/bevy/render/primitives/struct.Frustum.html#method.intersects_obb) seems like a very helpful function for implementing camera frustum based culling:

However, it is difficult to figure out how to use, due to the lack of documentation:

* where should `model_to_world` come from?

* are there any conditions on the kind of `aabb` expected (should it be in NDC, for instance?)