injectScript(doc, section) {
    let script = doc.createElement("script");
    script.setAttribute("type", "text/javascript");
    script.setAttribute("src", this.settings.script);
    script.textContent = " "; // Needed to prevent self closing tag

    doc.getElementsByTagName("head")[0].appendChild(script);
  }
Hook to handle injecting scripts before
a Section is serialized
@param  {document} doc
@param  {Section} section
@private