Add repo file tree item link behavior (#34730)

Converts the repo file tree items into `<a>` elements to have default
link behavior. Dynamic content load is still done when no special key is
pressed while clicking on an item.

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/components/DiffFileTree.vue

@@ -60,8 +60,8 @@ function updateState(visible: boolean) {
 </script>
 
 <template>
+  <!-- only render the tree if we're visible. in many cases this is something that doesn't change very often -->
   <div v-if="store.fileTreeIsVisible" class="diff-file-tree-items">
-    <!-- only render the tree if we're visible. in many cases this is something that doesn't change very often -->
     <DiffFileTreeItem v-for="item in store.diffFileTree.TreeRoot.Children" :key="item.FullName" :item="item"/>
   </div>
 </template>