Insert and safely resolve variables in Lexxy rich text. The gem gives you an editor button (and a `{{` prompt) for inserting variables, each stored as an Action Text attachment chip rather than literal markup, and resolves each chip to its value at render time. Register new chip types with `register_attachment`: a :value chip resolves to an escaped string, a :fragment chip splices rich content in before sanitization. Liquid is optional. The default renderer is plain, injection-safe string substitution and pulls in no template engine.