title: Django not appending slash to admin URL
body: <p>I'm using Django for my project's backend, and React on the frontend. As such, I have to specify a fallback URL which serves up index.html, which contains the script for all of my frontend code. </p>
  
  <p>However I want Django to match <code>admin</code> and <code>admin/</code>. The Regex below solves the problem, but accessing <code>admin</code> doesn't append a slash (I have APPEND_SLASH set to True in settings). The result is ugly looking urls like <code>adminapis</code> instead of <code>admin/apis</code> when I am using the admin interface.</p>
  
  <p>Any idea how I can preserve the trailing slash?</p>
  
  <pre><code>urlpatterns = [
      re_path(r"admin/?", admin.site.urls),
      path("", include("api.urls", namespace="api")),
      re_path(r".*", TemplateView.as_view(template_name="index.html")),
  ]
  </code></pre>