- Updated the documentation about shadow matte and SSShadow and RTShadows. (#2339)

* - Updated the documentation about shadow matte and SSShadow and RTShadows.

* Update CHANGELOG.md

Co-authored-by: sebastienlagarde <[email protected]>

Author: anisunity

com.unity.render-pipelines.high-definition/Documentation~/Master-Node-Unlit.md

@@ -54,7 +54,7 @@ To view these properties, click the **Cog** icon in the top right of the master
 | **DepthTest**    					|Unity uses DepthTest when rendering an object, to check if it is behind another object. Unity does this by testing the Z-value of a given Objects pixel and comparing against a value stored in the Z-buffer. By default, DepthTest is set to Less Equal, allowing the original object to appear in front of the object it is tested against. Use the drop-down to select the comparison function to use for the depth test. Each comparison function changes how the Shader renders. To expose this option, select **Transparent** from the **Surface Type** drop-down. <br/>&#8226; **Disabled:** Do not perform a ZTest. <br/>&#8226; **Never:** The ZTest is never passed. <br/>&#8226; **Less:** The ZTest passes if the pixels Z-value is less than the stored value. <br/>&#8226; **Equal:** The ZTest passes if the pixels Z-value is equal to the stored value. <br/>&#8226; **Less Equal:** The ZTest passes if the pixels Z-value is less than or equal than the Z-buffers value. This renders the tested pixel in front of the other. <br/>&#8226; **Greater:** The ZTest passes if the pixels Z-value is greater than the stored value. <br/>&#8226; **Not Equal:** The ZTest passes if the pixels Z-value is not equal to the stored value. <br/>&#8226; **Greater Equal:** The ZTest passes if the pixels Z-value is greater than or equal to the stored value. <br/>&#8226; **Always:** The ZTest always passes, there is no comparison to the stored value.|
 | **Double Sided**     						|Enable or disable whether or not the Shader should be rendered on both sides of a geometry.|
 | **Alpha Clipping**                 		|Enable the checkbox to make this Material act like a [Cutout Shader](https://docs.unity3d.com/Manual/StandardShaderMaterialParameterRenderingMode.html). Enabling this feature exposes more properties. For more information about the feature and for the  list of properties this feature exposes, see the [Alpha Clipping documentation](Alpha-Clipping.md).|
-| **Shadow Matte**                          |Enable or disable whether or not the Shader receive the shadow.|
+| **Shadow Matte**                          |Indicates whether or not the Shader receives shadows. Shadow matte only supports shadow maps. It does not support Screen Space Shadows, [Ray-Traced Shadows](Ray-Traced-Shadows.md), or [Contact Shadows](Override-Contact-Shadows.md).|
 | **Override ShaderGUI**                  |Lets you override the [ShaderGUI](https://docs.unity3d.com/ScriptReference/ShaderGUI.html) that this Shader Graph uses. If `true`, the **ShaderGUI** property appears, which lets you specify the ShaderGUI to use. |
 | **- ShaderGUI**                           |The full name of the ShaderGUI class to use, including the class path.|