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/skybox.rs

@@ -22,6 +22,9 @@ impl Plugin for SkyboxPlugin {
                     .run_if(skybox_assets_loaded),
             ),
         );
+
+        #[cfg(feature = "wasm")]
+        app.add_systems(Update, wasm::set_skybox_from_frontend);
     }
 }
 
@@ -112,3 +115,26 @@ impl SkyboxPaths {
         }
     }
 }
+
+#[cfg(feature = "wasm")]
+mod wasm {
+    use bevy::prelude::*;
+    use wasm_bindgen::prelude::*;
+
+    use crate::wasm::{StaticBuffer, WasmMessageBuffer};
+
+    use super::SkyboxId;
+
+    static SKYBOX_REQUEST: WasmMessageBuffer<String> = WasmMessageBuffer::new();
+
+    #[wasm_bindgen(js_name = setSkybox)]
+    pub fn set_skybox(id: &str) {
+        SKYBOX_REQUEST.write_message(id.to_string());
+    }
+
+    pub(super) fn set_skybox_from_frontend(mut cmd: Commands) {
+        if let Some(id) = SKYBOX_REQUEST.take_message() {
+            cmd.insert_resource(SkyboxId(id));
+        }
+    }
+}