/code> field in the <code>Dockerfile</code> could be a previously made image you or someone else has already created, allowing you to layer on top. The first example above is available via a public Google Continer Registry called <code>gcer-public</code>, made for this purpose, which you can see here: <code>https://console.cloud.google.com/gcr/images/gcer-public?project=gcer-public</code></p>
<p><img src="build-trigger-menu.png"></p>
<p>One example is <code>shiny-googleauthrdemo</code> - to construct the co