add /assets as root dir of public files (#15219)

* add `/assets` as root dir of public files

Signed-off-by: a1012112796 <1012112796@qq.com>

* move serviceworker.js

* make fmt

* fix some link

* fix test

* Apply suggestions from code review

Co-authored-by: silverwind <me@silverwind.io>

* Apply suggestions from code review

Co-authored-by: silverwind <me@silverwind.io>

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>

web_src/js/features/serviceworker.js

@@ -35,7 +35,7 @@ export default async function initServiceWorker() {
       // the spec strictly requires it to be same-origin so it has to be AppSubUrl to work
       await Promise.all([
         checkCacheValidity(),
-        navigator.serviceWorker.register(`${AppSubUrl}/serviceworker.js`),
+        navigator.serviceWorker.register(`${AppSubUrl}/assets/serviceworker.js`),
       ]);
     } catch (err) {
       console.error(err);