[v3] fix first item in FileTree not within permitted parent element (#3212)

* [v3] fix first item in `FileTree` not within permitted parent element

* Update packages/nextra/src/client/components/file-tree.tsx

---------

Co-authored-by: Dimitri POSTOLOV <dmytropostolov@gmail.com>

Author: 87xie

.changeset/empty-bottles-study.md

@@ -0,0 +1,7 @@
+---
+'nextra-theme-blog': patch
+'nextra-theme-docs': patch
+'nextra': patch
+---
+
+Fix first list item in `<FileTree>` not within permitted parent elements

packages/nextra/src/client/components/file-tree.tsx

@@ -31,9 +31,9 @@ function Tree({ children }: { children: ReactNode }): ReactElement {
         '_not-prose' // for nextra-theme-blog
       )}
     >
-      <div className="_inline-block _rounded-lg _border _px-4 _py-2 dark:_border-neutral-800">
+      <ul className="_inline-block _rounded-lg _border _px-4 _py-2 _border-neutral-200/70 contrast-more:_border-neutral-400 dark:_border-primary-100/10 contrast-more:dark:_border-neutral-400">
         {children}
-      </div>
+      </ul>
     </div>
   )
 }