Choreograph 1.0.0: release prep

- Update header date, add fx/fxbetween to header commands
- ScriptKit registration: expanded changelog, added fx/fxbetween commands,
  signals API, castName template var, fixed loop/chain docs accuracy
- README: added When section, fx/fxbetween, castName, sync row commands,
  signals API, accurate looping/chaining docs, full changelog
- script.json: clean description with feature summary and commands