Wled sound improvements

Starting from the original project I made a few improvements:

- the four towers with just a thinner wall. The original was 2mm wide, this one is 1mm. I printed in PLA+ and they're sturdy enough, while being thinner some more light pass through.

- tower are super wobbly once placed since tolerances are quite high. So I made a cover base with a slightly thinner tolerances and this keeps much better in place.

- finally, in case towers are still wobbly, I made a "raiser" that you can insert on top of the cover: having a 3mm higher border on the towers, helps keeping them in place.