I have a style tag with css properties added with [insertRule](https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleSheet/insertRule) function.

I tried `Element.cloneNode(tree)`, but it does not contain the cssRules

```js
// Add a style tag to head
var style = document.createElement("style");
style.id = "style",
style.type = "text/css",
document.head.appendChild(style);

// Insert some stylesheet rules
var sheet = style.sheet;
sheet.insertRule("p {background-color: red}", sheet.cssRules.length);
sheet.insertRule("p {color: white}", sheet.cssRules.length);
console.log(style.sheet); //Display an object with Css rules

// Try to clone
var styleClone = style.cloneNode(true);
console.log(styleClone.sheet); //Display null !
```

I expect `styleClone.sheet` to be equal to `style.sheet`