scmJS docs

Where things are documented

Each topic has one place it is written down:

Topic Where
What the editor does, for map makers guide.md; the README is the short version
What is in a map file and what the editor does with it file-formats.md
Where the graphics come from, data sets, how they are drawn game-data.md
Using, installing and writing plugins, the plugin API plugins.md, and the generated reference at docs.scmjs.dev/api
TrigScript, the trigger scripting language trigscript.md for map makers; the TrigScript plugin's README for the compiler and the commands it offers other plugins
Each plugin's internals its own repository's README
Running, building, releasing, contributing this file
Per-subsystem implementation notes CLAUDE.md
Provenance of adapted code and data ATTRIBUTION.md
Release notes docs/releases/