docs: add Arcane Towers wiki Replaces the welcome page with the player guide: how the four sealed tower dungeons generate and where, which tower rises in which biome, the climb and the 30-block drop into the dungeon below, the Exit Stone and what the seal means, the loot tables, and compatibility including the Expedition Core server settings that affect the towers. Co-Authored-By: Claude <noreply@anthropic.com>