Added 'Take a tour' button

src/landing/index.css

@@ -103,3 +103,9 @@
   font-size: 12px;
   padding-top: 8px;
 }
+
+.jp-Landing-tour {
+    color: #f37a3c;
+    margin-top: 20px;
+    cursor: pointer;
+}

src/landing/plugin.ts

@@ -80,6 +80,9 @@ function activateLanding(app: Application, services: ServiceManager): void {
   tour.textContent = 'Take a tour';
   tour.className = 'jp-Landing-tour';
   dialog.appendChild(tour);
+  tour.addEventListener('click', () => {
+    app.commands.execute('about-jupyterlab:show');
+  });
 
   img = body.getElementsByClassName('jp-ImageConsole')[0];
   img.addEventListener('click', () => {