feat(#6): Add PWA functionality and service worker

src/loadServiceWorker.ts

@@ -0,0 +1,28 @@
+export default function loadServiceWorker() {
+  let deferredPrompt;
+
+  window.addEventListener('beforeinstallprompt', (e) => {
+    const installApp = document.getElementById('install-offline-app');
+
+    installApp.addEventListener('click', async () => {
+      if (deferredPrompt !== null) {
+        deferredPrompt.prompt();
+        const { outcome } = await deferredPrompt.userChoice;
+        if (outcome === 'accepted') {
+          deferredPrompt = null;
+        }
+      }
+    });
+
+    document.getElementById('install-app-btn-container').style.display = 'block';
+    deferredPrompt = e;
+  });
+
+  window.addEventListener('load', () => {
+    navigator.serviceWorker.register('/service-worker.js');
+  });
+
+  if (window.matchMedia('(display-mode: standalone)').matches) {
+    document.getElementById('install-app-btn-container').style.display = 'none';
+  }
+}