Provide option to open the demo page in new tab.

layouts/scripts/toolbar/images/icon-open-new-tab.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" height="48" width="48" fill="#21252d">
+  <path
+    d="M9.5 43.05q-1.85 0-3.2-1.35t-1.35-3.2v-29q0-1.9 1.35-3.25T9.5 4.9h13.35v4.6H9.5v29h29V25.15h4.6V38.5q0 1.85-1.35 3.2t-3.25 1.35ZM20.3 30.9l-3.15-3.2 18.2-18.2h-9.5V4.9H43.1v17.25h-4.6V12.7Z"/>
+</svg>

layouts/scripts/toolbar/publish.jsx

@@ -39,7 +39,7 @@ function Publish(props = {}) {
 export function setupPublish(rootAttributes) {
   // INIT
   const wrapper = document.createElement('div');
-  document.querySelector('.page_toolbar__right').prepend(wrapper)
+  document.querySelector('.page_toolbar__right').append(wrapper)
 
   const root = ReactDOM.createRoot(wrapper);
   const html = (<Publish rootAttributes={rootAttributes}/>);