feat: implement Sleepy sleep diary

public/sw.js

@@ -0,0 +1,17 @@
+const CACHE = 'sleepy-v1';
+const ASSETS = ['/', '/manifest.webmanifest', '/favicon.svg'];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(caches.open(CACHE).then((cache) => cache.addAll(ASSETS)));
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(caches.keys().then((keys) => Promise.all(keys.filter((key) => key !== CACHE).map((key) => caches.delete(key)))));
+  self.clients.claim();
+});
+
+self.addEventListener('fetch', (event) => {
+  if (event.request.method !== 'GET') return;
+  event.respondWith(fetch(event.request).catch(() => caches.match(event.request).then((cached) => cached ?? caches.match('/'))));
+});