Add background music for intro-tv

[DanMorriss]

This should be th final code for the CSS:

.sound-buttons {
  position: absolute;
  left: 2rem;
  top: 1rem;
  color: white;
  font-size: 2rem;
  z-index: 3;
}

.sound-buttons i {
  color: var(--clr-neon-green);
}

.sound-buttons i:hover {
  cursor: pointer;
  transform: scale(1.1) rotate(-4deg);
}

.hide {
  display: none !important;
}