beevee: add library to workspace

This is designed to be the new BVH for the raytracer.

beevee/src/aabb/bounding_box.rs

@@ -0,0 +1,5 @@
+//! An Axis-Alighned Bounding Box.
+
+/// An axis-aligned bounding box.
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub struct AABB {}

beevee/src/aabb/mod.rs

@@ -0,0 +1,4 @@
+//! The module relating to Axis-Aligned Bounding Boxes.
+
+mod bounding_box;
+pub use bounding_box::*;