Add PWA offline support for standalone web app install

public/manifest.json

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+{
+    "short_name": "Meshtastic",
+    "name": "Meshtastic web interface",
+    "icons": [
+      {
+        "src": "icon.svg",
+        "sizes": "64x64 32x32 24x24 16x16",
+        "type": "image/x-icon"
+      }
+    ],
+    "start_url": ".",
+    "display": "standalone",
+    "theme_color": "#000000",
+    "background_color": "#ffffff"
+  }

src/service-worker.ts

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+/// <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.