add unity doc.

unity/PICO-Unity-Integration-SDK-release_3.4.0/SpatialAudio/Samples/scripts/GeomNumPrinter.cs

@@ -0,0 +1,15 @@
+using UnityEngine;
+
+public class GeomNumPrinter : MonoBehaviour
+{
+    public PXR_Audio_Spatializer_Context spatialAudioContext = null;
+
+    // Update is called once per frame
+    void Update()
+    {
+        if (spatialAudioContext)
+        {
+            Debug.Log("GetNumOfGeometries() == " + spatialAudioContext.GetNumOfGeometries());
+        }
+    }
+}