The autoresize attribute, when set to true, causes the editor's height to automatically scale to the fit the content inside. The editor's height will match that of the content, with height increasing and decreasing as the content changes. Vertical scrollbars will never appear.
This option was introduced in Textbox.io release 2.4.1
Enabling autoresize will automatically enable ui.toolbar.sticky, unless overridden, to ensure the toolbar is still usable if the editor grows taller than the window.