Add Google Analytics gtag snippet

Author: thomasahle

src/app.html

@@ -9,6 +9,14 @@
     <meta property="og:site_name" content="SV Tutorial" />
     <meta property="og:type" content="website" />
     <meta property="og:image" content="https://thomasnormal.github.io/sv-tutorial/favicon.svg" />
+    <!-- Google tag (gtag.js) -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id=G-S7J2WQBFPM"></script>
+    <script>
+      window.dataLayer = window.dataLayer || [];
+      function gtag() { dataLayer.push(arguments); }
+      gtag('js', new Date());
+      gtag('config', 'G-S7J2WQBFPM');
+    </script>
     <script>
       (function () {
         var dm = localStorage.getItem('svt:darkMode');