[Violation] Avoid using document.write()

This is coming from:
```
    if (doc.body.children.length < 1) {
         doc.open('text/html', 'replace');
         doc.write(this.props.initialContent);
         doc.close();
    }
```

In Firefox this is an error and the frame won't load: `DOMException: "The operation is insecure."`

