Update HTKToMRTKPortingGuide.md

Author: cre8ivepark

Documentation/HTKToMRTKPortingGuide.md

@@ -108,6 +108,7 @@ Some events no longer have unique events and now contain a MixedRealityInputActi
 |                           | HTK 2017 |  MRTK v2  |
 |---------------------------|----------|-----------|
 | Button                     | [Interactable Objects](https://github.com/Microsoft/MixedRealityToolkit-Unity/blob/htk_release/Assets/HoloToolkit-Examples/UX/Readme/README_InteractableObjectExample.md) | [Button](/Documentation/README_Button.md) |
+| Interactable                     | [Interactable Objects](https://github.com/Microsoft/MixedRealityToolkit-Unity/blob/htk_release/Assets/HoloToolkit-Examples/UX/Readme/README_InteractableObjectExample.md) | [Interactable](/Documentation/README_Interactable.md) |
 | Bounding Box             | [Bounding Box](https://github.com/Microsoft/MixedRealityToolkit-Unity/blob/htk_release/Assets/HoloToolkit-Examples/UX/Readme/README_BoundingBoxGizmoExample.md) | [Bounding Box](/Documentation/README_BoundingBox.md) |
 | App Bar             | [Bounding Box](https://github.com/Microsoft/MixedRealityToolkit-Unity/blob/htk_release/Assets/HoloToolkit-Examples/UX/Readme/README_BoundingBoxGizmoExample.md) | [App Bar](/Documentation/README_AppBar.md) |
 | One Hand Manipulation (Grb and Move)   | [HandDraggable](https://github.com/Microsoft/MixedRealityToolkit-Unity/blob/htk_release/Assets/HoloToolkit/Input/Scripts/Utilities/Interactions/HandDraggable.cs) | [Manipulation Handler](/Documentation/README_ManipulationHandler.md) |