fix(demo): add github branch

Author: javier-godoy

src/test/java/com/flowingcode/vaadin/addons/gridhelpers/GridHelpersDemoView.java

@@ -21,6 +21,7 @@
 package com.flowingcode.vaadin.addons.gridhelpers;
 
 import com.flowingcode.vaadin.addons.DemoLayout;
+import com.flowingcode.vaadin.addons.GithubBranch;
 import com.flowingcode.vaadin.addons.GithubLink;
 import com.flowingcode.vaadin.addons.demo.TabbedDemo;
 import com.vaadin.flow.component.dependency.StyleSheet;
@@ -30,6 +31,7 @@
 @SuppressWarnings("serial")
 @ParentLayout(DemoLayout.class)
 @Route("grid-helpers")
+@GithubBranch("1.x")
 @GithubLink("https://github.com/FlowingCode/GridHelpers")
 @StyleSheet("context://gridhelpers/styles.css")
 public class GridHelpersDemoView extends TabbedDemo {