Add whole-world VFX when the Stones awaken

[bilalakil]

This is to contribute to the surprise and intensity that the game aims to have players experience when witnessing the Stones awaken for the first time, and the overall duality aspect.

We already have a sound that plays, and a modification to the music track that's playing. #9 is going to change the UI too. Some in-world changes would be the icing on the cake here.

• An initial flash occurs at the moment they awaken. This should also cover the UI so players don't see the moment that it changes.
• A persistent particle effect adds more life to the world and makes it feel a little bit different.
  • Some other subtle effects like a tint may help here. Post-processing effects, maybe? (I've been trying to avoid them to keep the game very simple on the rendering side, but that's a strange requirement)