tutorial: replace white noise with ordered dithering.

tutorial/03_noise.lolfx

@@ -91,7 +91,8 @@ void main(void)
     float test = tmp.x * tmp.y + sin(3.0 * u_Time);
 
     /* Add some garbage noise */
-    test += fract(sin(test * 938.437) * 137.0) / 2.0;
+    vec2 d = vec2(16.0, 9.0) * pass_Position;
+    test += 0.5 * (length(fract(d) - 0.5) - length(fract(d + 0.5) - 0.5));
 
     vec3 points[4] = (test > 0.0) ? fire : water;