Announcing the Textbundle Format
The Textbundle format is very simple. A folder containing a plain text file, a JSON data file, and an assets sub-folder. An app, such as Ulysses, can write a Textbundle out and pass it to Marked, and all of the necessary components are automatically included. Images, additional text files, and any metadata needed are all there and safe from sandboxing restrictions.
Sandboxing is the primary motivation, and Textbundle solves the major issue of referencing external files in Markdown.
