implement language dropdown menu

Author: Guanran928

layouts/partials/menu.html

@@ -15,8 +15,13 @@
     <ul class="flex gap-2">
       {{- partial "inline/menu/walk.html" (dict "page" $page "menuEntries" .) }}
     </ul>
-    <!-- TODO: -->
-    语言
+    <select onchange="location = this.value;">
+      {{ range $page.Sites }}
+        <option value="{{ .Home.RelPermalink }}" {{ if eq $page.Site.Language.Lang .Language.Lang }}selected{{ end }}>
+          {{ .Language.LanguageName }}
+        </option>
+      {{ end }}
+    </select>
   </nav>
 {{- end }}