service worker: use injectManifest

- a RPC framework is added for further use
- fix an error that the service worker is not
    registered until the settings opened
- added theme-color
- settings: added a item to indicate the offline
    availablity

src/serviceworker/main.ts

@@ -0,0 +1,35 @@
+import { cleanupOutdatedCaches, precacheAndRoute } from "workbox-precaching";
+import { clientsClaim } from "workbox-core";
+import type { AnyCall } from "./services";
+
+function checkServiceWorker(
+  self: WorkerGlobalScope,
+): self is ServiceWorkerGlobalScope {
+  return !!(self as unknown as ServiceWorkerGlobalScope).registration;
+}
+
+if (checkServiceWorker(self)) {
+  cleanupOutdatedCaches();
+  precacheAndRoute(self.__WB_MANIFEST, {
+    cleanURLs: false
+  });
+
+  // auto update
+  self.skipWaiting();
+  clientsClaim();
+} else {
+  throw new TypeError("This entry point must be run in a service worker");
+}
+
+self.addEventListener("message", (event: MessageEvent<AnyCall>) => {
+  if (event.data.method === "ping") {
+    event.source.postMessage({id: event.data.id, jsonrpc: "2.0", result: undefined})
+  } else {
+    event.source.postMessage({
+      error: {
+        code: -32601,
+        message: "Method not found"
+      }
+    })
+  }
+})