Upgrade to Bevy v0.12 (#12)

* Migrate `System::pipe(...)` calls to `System::map(...)`
* Migrate `EventReader::iter()` and `EventReader::into_iter()` calls to
  `EventReader::read()`
* Migrate asset handling
* Generate `*.meta` files for assets
* Migrate a shader import
* Fix emissive materials double-applying their emissive strength
* Fix non-normalized bone weights resulting in incorrect vertex positions
* Set shadow filtering to `Hardware2x2` to mitigate increase in shader
  compilation times

studio/src/viewport.rs

@@ -78,7 +78,7 @@ pub mod wasm {
         mut events: EventReader<ViewportResizeEvent>,
         mut window: Query<&mut Window>,
     ) {
-        if let Some(event) = events.into_iter().last() {
+        if let Some(event) = events.read().last() {
             let ViewportSize { width, height } = event.0;
             window.single_mut().resolution.set(width, height);
         }