JS refactors (#22227)

- Replace all default exports with named exports, except for Vue SFCs
- Remove names from Vue SFCs, they are automatically inferred from the
filename
- Misc whitespace-related tweaks

web_src/js/features/repo-diff-filetree.js

@@ -2,7 +2,7 @@ import {createApp} from 'vue';
 import DiffFileTree from '../components/DiffFileTree.vue';
 import DiffFileList from '../components/DiffFileList.vue';
 
-export default function initDiffFileTree() {
+export function initDiffFileTree() {
   const el = document.getElementById('diff-file-tree');
   if (!el) return;