Merge pull request #24880 from inductor/add_eu2021

Add link to KubeCon Virtual EU 2021

Author: k8s-ci-robot

content/en/_index.html

@@ -44,6 +44,11 @@ <h2>The Challenges of Migrating 150+ Microservices to Kubernetes</h2>
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         <a href="https://events.linuxfoundation.org/kubecon-cloudnativecon-north-america/?utm_source=kubernetes.io&utm_medium=nav&utm_campaign=kccncna20" button id="desktopKCButton">Attend KubeCon NA virtually on November 17-20, 2020</a>
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+        <a href="https://events.linuxfoundation.org/kubecon-cloudnativecon-europe/?utm_source=kubernetes.io&utm_medium=nav&utm_campaign=kccnceu21" button id="desktopKCButton">Attend KubeCon EU virtually on May 4 – 7, 2021</a>
 </div>
 <div id="videoPlayer">
     <iframe data-url="https://www.youtube.com/embed/H06qrNmGqyE?autoplay=1" frameborder="0" allowfullscreen></iframe>