Move serviceworker to workbox and fix SSE interference

Instead of statically hardcoding every frontend asset, this uses a
type-based approach to cache all js,css and manifest.json requests.

This also fixes the issue that the service worker was interfering with
EventSource because it was unconditionally handling all requests which
this new implementation doesn't.

Fixes: https://github.com/go-gitea/gitea/issues/11092
Fixes: https://github.com/go-gitea/gitea/issues/7372

web_src/js/serviceworker.js

@@ -0,0 +1,14 @@
+import {registerRoute} from 'workbox-routing';
+import {StaleWhileRevalidate} from 'workbox-strategies';
+
+const cachedDestinations = new Set([
+  'manifest',
+  'script',
+  'style',
+  'worker',
+]);
+
+registerRoute(
+  ({request}) => cachedDestinations.has(request.destination),
+  new StaleWhileRevalidate({cacheName: 'static-cache-v2'}),
+);