Added note on decal emission on transparent surfaces (#567)

* Update Decal-Projector.md

* Update Decal-Projector.md

* Update Decal-Projector.md

Author: JordanL8

com.unity.render-pipelines.high-definition/Documentation~/Decal-Projector.md

@@ -45,4 +45,5 @@ Using the Inspector allows you to change all of the Decal Projector properties,
 ## Limitations
 
 - If you project a decal onto a transparent surface, HDRP ignores the decal's Texture tiling.
+- When you project a decal onto a surface, the emissive component of the decal affects the surface regardless of whether you enable **Receive Decal** on the surface's Material or not.
 - In **Project Settings > Graphics**, if **Instancing Variants** is set to **Strip All**, Unity strips the Decal Shader this component references when you build your Project. This happens even if you include the Shader in the **Always Included Shaders** list. If Unity strips the Shader during the build process, the decal does not appear in your built Application.