Add PWA support with service worker, manifest, and offline page

public/sw.js

@@ -0,0 +1,47 @@
+"use strict";
+
+const CACHE_NAME = "offline-cache-v1";
+const OFFLINE_URL = '/offline.html';
+
+const filesToCache = [
+    OFFLINE_URL
+];
+
+self.addEventListener("install", (event) => {
+    event.waitUntil(
+        caches.open(CACHE_NAME)
+            .then((cache) => cache.addAll(filesToCache))
+    );
+});
+
+self.addEventListener("fetch", (event) => {
+    if (event.request.mode === 'navigate') {
+        event.respondWith(
+            fetch(event.request)
+                .catch(() => {
+                    return caches.match(OFFLINE_URL);
+                })
+        );
+    } else {
+        event.respondWith(
+            caches.match(event.request)
+                .then((response) => {
+                    return response || fetch(event.request);
+                })
+        );
+    }
+});
+
+self.addEventListener('activate', (event) => {
+    event.waitUntil(
+        caches.keys().then((cacheNames) => {
+            return Promise.all(
+                cacheNames.map((cacheName) => {
+                    if (cacheName !== CACHE_NAME) {
+                        return caches.delete(cacheName);
+                    }
+                })
+            );
+        })
+    );
+});