Always register PWA

This is required for installability.

app/javascript/retrospring/common.ts

@@ -1,10 +1,12 @@
 import '@hotwired/turbo-rails';
 import initializeBootstrap from './initializers/bootstrap';
+import initializeServiceWorker from './initializers/serviceWorker';
 import initializeStimulus from './initializers/stimulus';
 
 export default function start(): void {
   try {
     initializeBootstrap();
+    initializeServiceWorker();
     initializeStimulus();
   } catch (e) {
     // initialization errors

app/javascript/retrospring/features/webpush/enable.ts

@@ -8,7 +8,7 @@ export function enableHandler (event: Event): void {
   const sender = event.target as HTMLButtonElement;
 
   try {
-    installServiceWorker()
+    getServiceWorker()
       .then(subscribe)
       .then(async subscription => {
         return Notification.requestPermission().then(permission => {
@@ -51,8 +51,8 @@ export function enableHandler (event: Event): void {
     }
 }
 
-async function installServiceWorker(): Promise<ServiceWorkerRegistration> {
+async function getServiceWorker(): Promise<ServiceWorkerRegistration> {
-  return navigator.serviceWorker.register("/service_worker.js", { scope: "/" });
+  return navigator.serviceWorker.getRegistration("/");
 }
 
 async function getServerKey(): Promise<Buffer> {

app/javascript/retrospring/initializers/serviceWorker.ts

@@ -0,0 +1,3 @@
+export default function (): void {
+  navigator.serviceWorker.register("/service_worker.js", { scope: "/" });
+}