sizeToContent property is not initialized from gs-size-to-content

The sizeToContent property of the gridstack items is not initialized from the gs-size-to-content attribute when gridstack is created from existing HTML content.

Your environment

• version of gridstack.js <= 11.1.0
• any browser

Steps to reproduce

Initialize the gridstack from existing HTML, set gs-size-to-content="true" to some item.

https://jsfiddle.net/mntg136x/1/

Expected behavior

Based on the documentation all item properties should be initialized from the HTML attributes.
See https://github.com/gridstack/gridstack.js/blob/master/doc/README.md#item-attributes