add pwa functionality

vite.config.js

@@ -1,6 +1,7 @@
 import {sveltekit} from "@sveltejs/kit/vite"
 import {defineConfig} from "vite"
+import {SvelteKitPWA} from "@vite-pwa/sveltekit"
 
 export default defineConfig({
-  plugins: [sveltekit()],
+  plugins: [sveltekit(), SvelteKitPWA()],
 })