add primitive cache busting, update service worker

lib/public/service-worker.js

@@ -1,9 +1,13 @@
+// Worker v1
+
 self.addEventListener('install', (event) => {
   event.waitUntil(
     caches.open('fb-to-ical').then((cache) => {
       return cache.addAll([
         '/',
         '/favicon.ico',
+        '/scripts.js?1',
+        '/style.css?1',
       ])
     })
   )
@@ -17,3 +21,9 @@ self.addEventListener('fetch', (event) => {
       })
   )
 })
+
+self.addEventListener('message', (event) => {
+  if (event.data.action === 'skipWaiting') {
+    self.skipWaiting()
+  }
+})