BVH animation loading / retargeting (#25)

This PR adds support for BVH animation files, with a custom animation
player and retargeting solution for our Blender Rigify-based skeletal
meshes.

---------

Co-authored-by: Brooks Palin <brookspalin710@gmail.com>

studio/src/bvh/loader.rs

@@ -0,0 +1,37 @@
+use bevy::{
+    asset::{io::Reader, AssetLoader, AsyncReadExt, LoadContext},
+    utils::BoxedFuture,
+};
+
+use super::{
+    error::{Anyhow, Error},
+    Bvh,
+};
+
+#[derive(Default)]
+pub struct BvhLoader;
+
+impl AssetLoader for BvhLoader {
+    type Asset = Bvh;
+    type Settings = ();
+    type Error = Error;
+
+    fn load<'a>(
+        &'a self,
+        reader: &'a mut Reader,
+        _settings: &'a Self::Settings,
+        _cx: &'a mut LoadContext,
+    ) -> BoxedFuture<'a, Result<Self::Asset, Self::Error>> {
+        Box::pin(async move {
+            let mut buf = vec![];
+            reader.read_to_end(&mut buf).await.anyhow()?;
+            let bvh = studio_bvh::from_bytes(&buf).anyhow()?;
+
+            Ok(Bvh(bvh))
+        })
+    }
+
+    fn extensions(&self) -> &[&str] {
+        &["bvh"]
+    }
+}