Added release note for light widget path tracing

Documentation/release/dev/add-raytraced-lightwidget.md

+## Add vtkLightWidget to path-traced environments
+
+The `vtkRenderingRayTracing` module now supports rendering and interaction with the `vtkLightWidget`
+to be able to interactively place and modify lights in the view.
+
+![](https://vtk.org/files/ExternalData/SHA512/53b5e6ab5f30f59915be20da76fb415181d7fba709964f0d78de60bcc24abb860d2f339dfeaad26da8dfbe4f674617a65132ec442955c9ba9768d9c630693a8b)
+
+![](./lightwidget_pathtracing.png)