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

webpack.config.js

@@ -35,13 +35,20 @@ module.exports = {
     jquery: [
       resolve(__dirname, 'web_src/js/jquery.js'),
     ],
+    serviceworker: [
+      resolve(__dirname, 'web_src/js/serviceworker.js'),
+    ],
     icons: glob('node_modules/@primer/octicons/build/svg/**/*.svg'),
     ...themes,
   },
   devtool: false,
   output: {
     path: resolve(__dirname, 'public'),
-    filename: 'js/[name].js',
+    filename: ({chunk}) => {
+      // serviceworker can only manage assets below it's script path so we
+      // have to put it in / instead of /js/
+      return chunk.id === 'serviceworker' ? '[name].js' : 'js/[name].js';
+    },
     chunkFilename: 'js/[name].js',
   },
   optimization: {