Enable installing app as pwa

app/javascript/application.js

@@ -1,2 +1,3 @@
 // Configure your import map in config/importmap.rb. Read more: https://github.com/rails/importmap-rails
 import "controllers"
+import "custom/companion"

app/javascript/custom/companion.js

@@ -0,0 +1,11 @@
+if (navigator.serviceWorker) {
+  navigator.serviceWorker
+    .register("/service-worker.js", { scope: "/" })
+    .then(() => navigator.serviceWorker.ready)
+    .then((registration) => {
+      if ("SyncManager" in window) {
+        registration.sync.register("sync-forms");
+      }
+    })
+    .then(() => console.log("[Companion]", "Service worker registered!"));
+}