fix: Add missing service-worker to avoid 404

It's been removed in the current create-react-app, see
facebook/create-react-app#9776

src/service-worker.ts

@@ -0,0 +1,81 @@
+/// <reference lib="webworker" />
+/* eslint-disable no-restricted-globals */
+
+// This service worker can be customized!
+// See https://developers.google.com/web/tools/workbox/modules
+// for the list of available Workbox modules, or add any other
+// code you'd like.
+// You can also remove this file if you'd prefer not to use a
+// service worker, and the Workbox build step will be skipped.
+
+import { clientsClaim } from "workbox-core";
+import { ExpirationPlugin } from "workbox-expiration";
+import { precacheAndRoute, createHandlerBoundToURL } from "workbox-precaching";
+import { registerRoute } from "workbox-routing";
+import { StaleWhileRevalidate } from "workbox-strategies";
+
+declare const self: ServiceWorkerGlobalScope;
+
+clientsClaim();
+
+// Precache all of the assets generated by your build process.
+// Their URLs are injected into the manifest variable below.
+// This variable must be present somewhere in your service worker file,
+// even if you decide not to use precaching. See https://cra.link/PWA
+precacheAndRoute(self.__WB_MANIFEST);
+
+// Set up App Shell-style routing, so that all navigation requests
+// are fulfilled with your index.html shell. Learn more at
+// https://developers.google.com/web/fundamentals/architecture/app-shell
+const fileExtensionRegexp = new RegExp("/[^/?]+\\.[^/]+$");
+registerRoute(
+    // Return false to exempt requests from being fulfilled by index.html.
+    ({ request, url }: { request: Request; url: URL }) => {
+        // If this isn't a navigation, skip.
+        if (request.mode !== "navigate") {
+            return false;
+        }
+
+        // If this is a URL that starts with /_, skip.
+        if (url.pathname.startsWith("/_")) {
+            return false;
+        }
+
+        // If this looks like a URL for a resource, because it contains
+        // a file extension, skip.
+        if (url.pathname.match(fileExtensionRegexp)) {
+            return false;
+        }
+
+        // Return true to signal that we want to use the handler.
+        return true;
+    },
+    createHandlerBoundToURL(process.env.PUBLIC_URL + "/index.html")
+);
+
+// An example runtime caching route for requests that aren't handled by the
+// precache, in this case same-origin .png requests like those from in public/
+registerRoute(
+    // Add in any other file extensions or routing criteria as needed.
+    ({ url }) =>
+        url.origin === self.location.origin && url.pathname.endsWith(".png"),
+    // Customize this strategy as needed, e.g., by changing to CacheFirst.
+    new StaleWhileRevalidate({
+        cacheName: "images",
+        plugins: [
+            // Ensure that once this runtime cache reaches a maximum size the
+            // least-recently used images are removed.
+            new ExpirationPlugin({ maxEntries: 50 })
+        ]
+    })
+);
+
+// This allows the web app to trigger skipWaiting via
+// registration.waiting.postMessage({type: 'SKIP_WAITING'})
+self.addEventListener("message", (event) => {
+    if (event.data && event.data.type === "SKIP_WAITING") {
+        self.skipWaiting();
+    }
+});
+
+// Any other custom service worker logic can go here.