link element not append in head element in ediot.canvas #firefox #grapesjs

am trying to add google fonts in web-builder to change the font style for that to import am adding cdn in editor the code works in chrome and safari but firefox not working 

createLinkElement(fontFamily) {
        let link = document.createElement("LINK");
        link.setAttribute("rel", "stylesheet");
        link.setAttribute("href", `https://fonts.googleapis.com/css?family=${fontFamily}`);
        return link;
    }


editor.Canvas.getDocument().head.append(this.createLinkElement(fontFamily));

element also not appending