Doc the joint conversion method

Author: keveleigh

Assets/MixedRealityToolkit.Providers/WindowsMixedReality/XRSDK/Controllers/WindowsMixedRealityXRSDKArticulatedHand.cs

@@ -275,6 +275,16 @@ private void UpdateIndexFingerData(MixedRealityInteractionMapping interactionMap
             }
         }
 
+        /// <summary>
+        /// Converts a Unity finger bone into an MRTK hand joint.
+        /// </summary>
+        /// <remarks>
+        /// For HoloLens 2, Unity provides four joints per finger, in index order of metacarpal (0) to tip (4).
+        /// The first joint for the thumb is the wrist joint. Palm joint is not provided.
+        /// </remarks>
+        /// <param name="finger">The Unity classification of the current finger.</param>
+        /// <param name="index">The Unity index of the current finger bone.</param>
+        /// <returns>The current Unity finger bone converted into an MRTK joint.</returns>
         private TrackedHandJoint ConvertToTrackedHandJoint(HandFinger finger, int index)
         {
             switch (finger)