add outbound link umami analytics script

Author: gchartier

src/routes/+layout.svelte

@@ -6,12 +6,15 @@
 
 <!-- Setup Privacy-preserving Umami Analytics -->
 <svelte:head>
+    <!-- Umami base script -->
     <script
         async
         defer
         data-website-id="2d656c7d-b41a-4e19-934c-d7c9d91d784d"
         src="https://analytics.server.orcfax.io/umami.js"
     ></script>
+    <!-- Outbound-link helper -->
+    <script async defer src="/track-external.js"></script>
 </svelte:head>
 
 {@render children()}

static/track-external.js

@@ -0,0 +1,26 @@
+/* Auto-tag all external links for Umami */
+(() => {
+    const EVENT = "outbound-link-click";
+
+    function tagLinks() {
+        document.querySelectorAll("a").forEach((a) => {
+            if (
+                a.host !== window.location.host && // external
+                !a.hasAttribute("data-umami-event") // not already tagged
+            ) {
+                a.setAttribute("data-umami-event", EVENT);
+                a.setAttribute("data-umami-event-url", a.href);
+            }
+        });
+    }
+
+    // First run
+    tagLinks();
+
+    // Re-run after every client-side navigation
+    if (window.__sveltekit) {
+        import("$app/navigation").then(({ afterNavigate }) => {
+            afterNavigate(tagLinks);
+        });
+    }
+})();