ComposerMessage
ComposerMessage =
DocumentMessage|ModeMessage|SelectMessage
@ebitex/content-sdk/preview — the live-preview bridge protocol and a framework-agnostic
receiver. No React here: @ebitex/content-sdk/react’s <PreviewBridge> is built on this, and
Composer uses the same definitions for its sender side, so the two ends of the bridge share one
definition of every message.