Minecraft sky simulation

Add an option to simulate the Minecraft sky in Chunky. The sky should change according to the sun position, and even display stars and maybe the moon (and add a setting to change the moon phase?) when the sun is below the horizon. The color of the sky can be changed slightly using biome temperature and humidity settings, or any other factors that change the sky blueness, as in Minecraft, and the weather can also be changed, such as to rain or thunder, to make the sky gray.

The issue names no files, tests, or entry points. Start by locating Chunky's sky and environment rendering entry point, then determine which Minecraft sky behaviors are in scope. Done would require an agreed subset covering the requested day/night appearance and any selected weather, stars, moon, biome, or moon-phase behavior.

Written by the indexing model from the issue text.