admin: sidebar back home link

app/views/admins/shared/_sidebar.html.erb

@@ -1,10 +1,10 @@
 <% sidebar_collapse = request.cookies['admin_sidebar_collapse'].to_s == 'true' %>
 <nav id="sidebar" class="<%= sidebar_collapse ? 'active' : '' %>" data-current-controller="<%= admin_sidebar_controller %>">
   <div class="sidebar-header">
-    <div class="sidebar-header-logo">
+    <a href="/" class="sidebar-header-logo" data-toggle="tooltip" data-title="返回主站" >
       <img class="rounded-circle" src="/images/<%= url_to_avatar(current_user) %>" />
       <span class="logo-label">后台管理</span>
-    </div>
+    </a>
     <div id="sidebarCollapse" class="navbar-btn <%= sidebar_collapse ? 'active' : '' %>">
       <i class="fa fa-chevron-left fold" data-toggle="tooltip" data-placement="right" data-boundary="window" title="收起"></i>
       <i class="fa fa-bars unfold" data-toggle="tooltip" data-placement="right" data-boundary="window" title="展开"></i>