Use locally stored copy of `Window` object in `State`, instead of the global object.

src/lib/State.ts

@@ -28,7 +28,7 @@ export class State extends EventEmitter<{
   }
 
   private bindEvents(): void {
-    on(window, 'popstate', () => this.update());
+    on(this.#window, 'popstate', () => this.update());
   }
 
   getCollection(): Collection {