Add a custom event listener to a Textbox.io editor change event with editor.events.change.addlistener().
This API was introduced in Textbox.io release 2.3.0
You can detect when editor content changes by attaching a callback function to the editor’s change event.
Example
editor.events.change.addListener(callback)
// Add a custom event listener to the editor change event
editor.events.change.addListener(function() {
    alert('Editor content has changed.');
});
Parameters
| callback | Function | Function executed when the editor content changes. | 
Returns
No return value.