Added URP outline issue to the doc as a known issue. (#308)

Author: H3idi-X

com.unity.toonshader/Documentation~/Known-issue.md

@@ -4,3 +4,12 @@
 
 The **Unity Toon Shader** [Outline](Outline.md) isn't automatically disabled when recording with  [AOV Image Sequence Recorder](https://docs.unity3d.com/Packages/[email protected]/manual/RecorderAOV.html), Please disable [Outline](Outline.md#outline) in Material Inspectors when outputting AOV Images.
 
+## When using Universal Render Pipeline
+
+When using [Universal Render Pipeline](https://docs.unity3d.com/Manual/com.unity.render-pipelines.universal.html), you need to set [Depth Priming Mode](https://docs.unity3d.com/Packages/[email protected]/manual/urp-universal-renderer.html#rendering) disabled to show [outline](Outline.md).
+
+
+| Depth Priming Mode Auto | Depth Priming Mode Disabled | 
+| ---- | ---- |
+| <img src="images/DepthPrimingModeAuto.png" > | <img src="images/DepthPrimingModeDisabled.png" > |
+<br>