Single-object viewer POC (#14)

This commit implements a Sketchfab-style single-object viewer as a minimal
proof-of-concept.

### `@storyteller/studio-web`
This is a new package to house web components for interfacing with the
`@storyteller/studio` WASM library. It currently includes a single component,
`<sts-viewer />`, which is exported from `@storyteller/studio-web/viewer`.

### `react-frontend`
This is a new application intended as a proof-of-concept and testbed for React
interop with `@storyteller/studio-web`.

Web components are currently a little bit fiddly to use in a React application.
`react-frontend/src/app/studio-viewer.tsx` demonstrates how a React-idiomatic
component can be written as a thin wrapper around a web component, and
`react-frontend/src/app/app.tsx` demonstrates that wrapper component in use.

studio/src/debug.rs

@@ -7,11 +7,18 @@ use bevy_mod_picking::debug::DebugPickingMode;
 use crate::{
     camera_controller::{CameraController, CameraMotionSystem},
     input::{Action, InputAction, Lifecycle},
+    MainCamera,
 };
 
 #[derive(Resource, Deref, DerefMut)]
 pub struct DebugMode(bool);
 
+#[derive(Component, Clone, Copy, Debug)]
+pub struct DebugPoint {
+    pub point: Vec3,
+    pub color: Color,
+}
+
 pub struct DebugPlugin;
 impl Plugin for DebugPlugin {
     fn build(&self, app: &mut App) {
@@ -31,7 +38,7 @@ impl Plugin for DebugPlugin {
                     toggle_debug_mode,
                     update_debug_picking_mode.run_if(resource_changed::<DebugMode>()),
                     update_gizmo_line_thickness,
-                    draw_world_axes
+                    (draw_world_axes, draw_debug_points)
                         .after(CameraMotionSystem)
                         .run_if(is_debug_mode),
                 ),
@@ -84,6 +91,23 @@ fn draw_world_axes(mut gizmos: Gizmos, q: Query<&CameraController>) {
     draw_axis(Vec3::Z, Color::BLUE);
 }
 
+fn draw_debug_points(
+    mut gizmos: Gizmos,
+    q_debug_points: Query<&DebugPoint>,
+    q_cam_xform: Query<&GlobalTransform, With<MainCamera>>,
+) {
+    let Ok(cam_xform) = q_cam_xform.get_single() else {
+        return;
+    };
+    for &DebugPoint { point, color } in q_debug_points.iter() {
+        let dist = cam_xform.translation().distance(point);
+        gizmos.cuboid(
+            Transform::from_translation(point).with_scale(Vec3::splat(dist / 300.)),
+            color,
+        );
+    }
+}
+
 #[rustfmt::skip]
 #[allow(dead_code)]
 pub fn write_mat3(w: &mut impl fmt::Write, m: &Mat3) -> fmt::Result {