feat: Introduce DownCount feature with new models, scripts, textures, and a dedicated quiz scene.

Assets/Quiz/Scripts/DownCount/LetterStand.cs

@@ -0,0 +1,9 @@
+
+using UdonSharp;
+using UnityEngine;
+using VRC.SDKBase;
+using VRC.Udon;
+
+public class LetterStand : UdonSharpBehaviour
+{
+}