Add umami

src/assets/index.html

@@ -9,6 +9,7 @@
         content="Rogier Lommers: I am an experienced Principal Tech Lead working for bol.com. I develop and maintain backend systems with focus on high availability, performance, reliability and scalability.">
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <script async defer src="https://tianji.lommers.org/tracker.js" data-website-id="clydb2w3n0001m406dzk6loit"></script>
+    <script defer src="https://umami.lommers.org/script.js" data-website-id="94a51c4e-40a1-4736-a853-af3371b7bd5e"></script>
 
     <style>
         @import url(https://fonts.googleapis.com/css?family=Lato:400,700,900);