basic service worker registration via workbox

ref #7

src/App.svelte

@@ -50,6 +50,18 @@
     "*": NotFound,
   };
   //
+  if ("serviceWorker" in navigator) {
+    window.addEventListener("load", () => {
+      navigator.serviceWorker.register("/sw.js").then(
+        (registration) => {
+          console.log(`sw successful with scope: ${registration.scope}`);
+        },
+        (err) => {
+          console.log(`sw failed: ${err}`);
+        }
+      );
+    });
+  }
 </script>
 
 <Router {routes} />