Updated samples module (added ray tracing tutorial)

Author: TheMostDiligent

DiligentCore

@@ -665,6 +665,7 @@ Please refer to [this page](https://github.com/DiligentGraphics/DiligentCore#api
 | [18 - Queries](https://github.com/DiligentGraphics/DiligentSamples/tree/master/Tutorials/Tutorial18_Queries) | ![](https://github.com/DiligentGraphics/DiligentSamples/blob/master/Tutorials/Tutorial18_Queries/Animation_Small.gif) | This tutorial demonstrates how to use queries to retrieve various information about the GPU operation, such as the number of primitives rendered, command processing duration, etc. |
 | [19 - Render Passes](https://github.com/DiligentGraphics/DiligentSamples/tree/master/Tutorials/Tutorial19_RenderPasses) | ![](https://github.com/DiligentGraphics/DiligentSamples/blob/master/Tutorials/Tutorial19_RenderPasses/Animation_Small.gif) | This tutorial demonstrates how to use the render passes API to implement simple deferred shading. |
 | [20 - Mesh Shader](https://github.com/DiligentGraphics/DiligentSamples/tree/master/Tutorials/Tutorial20_MeshShader) | ![](https://github.com/DiligentGraphics/DiligentSamples/blob/master/Tutorials/Tutorial20_MeshShader/Animation_Small.gif) | This tutorial demonstrates how to use amplification and mesh shaders, the new programmable stages, to implement view frustum culling and object LOD calculation on the GPU. |
+| [21 - Ray Tracing](https://github.com/DiligentGraphics/DiligentSamples/tree/master/Tutorials/Tutorial21_RayTracing) | ![](https://github.com/DiligentGraphics/DiligentSamples/blob/master/Tutorials/Tutorial21_RayTracing/Animation_Small.gif) | This tutorial demonstrates the basics of using ray tracing API in Diligent Engine. |
 
 <a name="samples"></a>
 # [Samples](https://github.com/DiligentGraphics/DiligentSamples)