adding clarity

_includes/head.html

@@ -76,6 +76,14 @@
 
   <script src="https://cdn.jsdelivr.net/combine/npm/popper.js@1.15.0,npm/bootstrap@4.0.0/dist/js/bootstrap.min.js" async></script>
 
+  <script type="text/javascript">
+      (function(c,l,a,r,i,t,y){
+          c[a]=c[a]||function(){(c[a].q=c[a].q||[]).push(arguments)};
+          t=l.createElement(r);t.async=1;t.src="https://www.clarity.ms/tag/"+i;
+          y=l.getElementsByTagName(r)[0];y.parentNode.insertBefore(t,y);
+      })(window, document, "clarity", "script", "4xpt5cebre");
+  </script>
+
   {% include js-selector.html %}
 
 </head>