Examples: Fix flickering in decals demo. (#26593)

examples/webgl_decals.html

@@ -267,6 +267,7 @@
 				material.color.setHex( Math.random() * 0xffffff );
 
 				const m = new THREE.Mesh( new DecalGeometry( mesh, position, orientation, size ), material );
+				m.renderOrder = decals.length; // give decals a fixed render order
 
 				decals.push( m );
 				scene.add( m );