integrity attribute to github button

Author: navaneethsnair1

src/main/content/_includes/head.html

@@ -72,7 +72,7 @@
       {% include_cached noindex.html %}
   {% endif %}
 
-  <script async defer src="https://buttons.github.io/buttons.js"></script>
+  <script async defer src="https://buttons.github.io/buttons.js" integrity="sha512-pBW60/IKtE8DJnbxxOaIVfRIKb27cnEG/JOFLMf7hkDWpohNZNrx+PmYw0fsJvQMK/sp5NzUYgZkIIv0FbeNjw==" crossorigin="anonymous"></script>
   <script type="text/javascript">
     window._ibmAnalytics = {
         "settings": {