v0.22.1

SpatialIndex frees its trees' native memory when they are replaced, and on close() (#72).

v0.22.0

• SceneGraph, Renderables and World throw when changed from a thread other than the owner named with scene.clock().ownedBy(thread) (#60).
• The scene's change log grows rather than drop a change made since the last update: consumers that keep up never rebuild, however many nodes change at once.

v0.21.0

• MeshData is AutoCloseable: closing frees its buffers at once (engine#101).
• AssetLoader.unload closes AutoCloseable data by default; the cache closes generated assets it evicts.
• API change: expandIndices(Arena).