add plausible analytics tag

Author: Sami Kolari

index.html

@@ -21,6 +21,10 @@
 
   </script>
   <!-- End Google Analytics -->
+
+  <!-- plausible.io -->
+  <script defer data-domain="robotframework.org" src="https://plausible.io/js/plausible.js"></script>
+
   <title>Robot Framework</title>
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">