docs: correct the billboard default and block centering Billboard tracking is now opt-in per part rather than the default, and block parts are centred on their position instead of hanging off it by a corner. Refs 3DEH-Lite#1.
Add documentation pages and refresh Home Add comprehensive docs: Commands-and-Permissions.md (commands, permissions, parts and attributes), Configuration.md (config.yml defaults, data.yml format and editing notes) and Developer-API.md (usage, manager API, threading, serialization). Update Home.md with an expanded overview, requirements, model, first steps and links to the new pages, and remove the obsolete ..md placeholder. These changes provide full user and developer guidance and clarify Folia/Paper compatibility and reload/edit workflows.