Examples: Improve post processing in normalmap demo. (#24943)

examples/webgl_materials_normalmap.html

@@ -143,7 +143,9 @@
 				effectColor.uniforms[ 'powRGB' ].value.set( 1.4, 1.45, 1.45 );
 				effectColor.uniforms[ 'mulRGB' ].value.set( 1.1, 1.1, 1.1 );
 
-				composer = new EffectComposer( renderer );
+				const renderTarget = new THREE.WebGLRenderTarget( window.innerWidth, window.innerHeight, { type: THREE.HalfFloatType, depthTexture: new THREE.DepthTexture() } );
+
+				composer = new EffectComposer( renderer, renderTarget );
 
 				composer.addPass( renderModel );
 				composer.addPass( effectFXAA );