support setting style keys

[samouri]

summary
In normal DOM, attributes of the style property will reflect in the attributes.

For example:

div.style.width = '100px';

This concept in general exists in WorkerDOM and is called a PropertyBackedAttribute.
This works for style when using explicit methods like setProperty, but does not work when directly assigning to `style.

conditions of satisfaction
Running div.style.width = '100px'; should result in setting style="width:100px;" on the div.