center the sensor around game object not root

com.unity.ml-agents/Runtime/Sensors/BoxOverlapChecker.cs

         Vector3Int m_GridSize;
         bool m_RotateWithAgent;
         LayerMask m_ColliderMask;
+        GameObject m_CenterObject;
         GameObject m_RootReference;
         string[] m_DetectableTags;
         int m_InitialColliderBufferSize;
             Vector3Int gridSize,
             bool rotateWithAgent,
             LayerMask colliderMask,
+            GameObject centerObject,
             GameObject rootReference,
             string[] detectableTags,
             int initialColliderBufferSize,
             m_GridSize = gridSize;
             m_RotateWithAgent = rotateWithAgent;
             m_ColliderMask = colliderMask;
+            m_CenterObject = centerObject;
             m_RootReference = rootReference;
             m_DetectableTags = detectableTags;
             m_InitialColliderBufferSize = initialColliderBufferSize;
         {
             if (m_RotateWithAgent)
             {
-                return m_RootReference.transform.TransformPoint(m_CellLocalPositions[cellIndex]);
+                return m_CenterObject.transform.TransformPoint(m_CellLocalPositions[cellIndex]);
-                return m_CellLocalPositions[cellIndex] + m_RootReference.transform.position;
+                return m_CellLocalPositions[cellIndex] + m_CenterObject.transform.position;
-            return m_RotateWithAgent ? m_RootReference.transform.rotation : Quaternion.identity;
+            return m_RotateWithAgent ? m_CenterObject.transform.rotation : Quaternion.identity;
         }
 
         /// <summary>
                 }
 
                 var closestColliderPoint = foundColliders[i].ClosestPointOnBounds(cellCenter);
-                var currentDistanceSquared = (closestColliderPoint - m_RootReference.transform.position).sqrMagnitude;
+                var currentDistanceSquared = (closestColliderPoint - m_CenterObject.transform.position).sqrMagnitude;
 
                 if (currentDistanceSquared >= minDistanceSquared)
                 {

com.unity.ml-agents/Runtime/Sensors/GridSensorComponent.cs

                 m_GridSize,
                 m_RotateWithAgent,
                 m_ColliderMask,
+                gameObject,
                 RootReference,
                 m_DetectableTags,
                 m_InitialColliderBufferSize,

com.unity.ml-agents/Tests/Runtime/Sensor/BoxOverlapCheckerTests.cs

             Vector3Int gridSize,
             bool rotateWithAgent,
             LayerMask colliderMask,
+            GameObject centerObject,
             GameObject rootReference,
             string[] detectableTags,
             int initialColliderBufferSize,
                 gridSize,
                 rotateWithAgent,
                 colliderMask,
+                centerObject,
                 rootReference,
                 detectableTags,
                 initialColliderBufferSize,
             int gridSizeX = 10,
             int gridSizeZ = 10,
             bool rotateWithAgent = true,
+            GameObject centerObject = null,
             GameObject rootReference = null,
             string[] detectableTags = null,
             int initialColliderBufferSize = 4,
                 new Vector3Int(gridSizeX, 1, gridSizeZ),
                 rotateWithAgent,
                 LayerMask.GetMask("Default"),
+                centerObject,
                 rootReference,
                 detectableTags,
                 initialColliderBufferSize,