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-web/src/index.ts

@@ -0,0 +1 @@
+export * from "./lib/viewer.element";

studio-web/src/lib/viewer.element.ts

@@ -0,0 +1,60 @@
+import * as studio from "@storyteller/studio";
+import { LitElement, PropertyValues, html, unsafeCSS } from "lit";
+import { customElement, property } from "lit/decorators.js";
+
+import styles from "./viewer.element.scss?inline";
+import { ViewportSize } from "@storyteller/studio";
+
+@customElement("sts-viewer")
+export class ViewerElement extends LitElement {
+	static override styles = unsafeCSS(styles);
+
+	@property() objectId?: string;
+	@property() skyboxId?: string;
+
+	protected override createRenderRoot(): Element | ShadowRoot {
+		return this;
+	}
+
+	protected override updated(changes: PropertyValues<this>): void {
+		if (!studio.isInitialized()) {
+			this.#startViewer();
+		} else {
+			if (changes.has("objectId") && !!this.objectId)
+				studio.loadObject(this.objectId);
+
+			if (changes.has("skyboxId") && !!this.skyboxId)
+				studio.setSkybox(this.skyboxId);
+		}
+	}
+
+	#startViewer(): void {
+		if (!this.objectId) return;
+		if (!this.skyboxId) return;
+
+		const width = window.innerWidth;
+		const height = window.innerHeight;
+		try {
+			studio.startViewer(
+				this.objectId,
+				this.skyboxId,
+				"#studio_canvas",
+				"Storyteller Studio",
+				new ViewportSize(width, height),
+			);
+		} catch (err) {
+			if (!(err as Error).message?.startsWith("Using exceptions for control flow"))
+				throw err;
+		}
+	}
+
+	protected override render = () => html`
+		<canvas id="studio_canvas" alt="Storyteller Studio"></canvas>
+	`;
+}
+
+declare global {
+	export interface HTMLElementTagNameMap {
+		"sts-viewer": ViewerElement;
+	}
+}