title: How can we avoid having to manually refresh the Sheet after our Add-on is installed?
body: <p>We have a few Google Sheets Add-ons and all of them require a reload of the Sheet in order for the Add-on to be used. The user installs it fine and it shows up in the Add-on menu but they are unable to actually use the Add-on until they reload the sheet. This happens for all of our users and in our own tests. We have:</p>
  
  <pre><code>function onInstall() {
    onOpen();
  }
  
  function onOpen() {
    SpreadsheetApp.getUi()
    .createAddonMenu()
    .addItem("Do something", "showSidebar")
    .addItem("Do something else", "showSidebar")
    .addToUi(); 
  }
  
  function showSidebar(){
    var html = HtmlService.createTemplateFromFile("myhtml");
    html = html.evaluate().setTitle("Our so great of a title");  
    SpreadsheetApp.getUi().showSidebar(html);
  }
  </code></pre>
  
  <p>Are we missing anything obvious that will load the menu automatically when the Add-on is installed. This is our general template and it happens with all of our Add-ons.</p>