Set stencilBuffer property of WebGLRenderTarget in WebXRManager (#24488)

Co-authored-by: Noeri Huisman <mrxz@users.noreply.github.com>

src/renderers/webxr/WebXRManager.js

@@ -285,7 +285,8 @@ class WebXRManager extends EventDispatcher {
 						{
 							format: RGBAFormat,
 							type: UnsignedByteType,
-							encoding: renderer.outputEncoding
+							encoding: renderer.outputEncoding,
+							stencilBuffer: attributes.stencil
 						}
 					);