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

vite.config.ts

@@ -16,10 +16,16 @@ export default defineConfig(({ mode }) => ({
       },
     }),
     VitePWA({
+      strategies: "injectManifest",
       registerType: "autoUpdate",
       devOptions: {
-        enabled: mode === "staging",
+        enabled: mode === "staging" || mode === "dev",
       },
+      srcDir: "src/serviceworker",
+      filename: "main.ts",
+      manifest: {
+        theme_color: "#673ab7"
+      }
     }),
     version(),
   ],