Add note telling people to refresh

lib/pleroma/web/templates/akkoma_api/frontend_switcher/switch.html.eex

@@ -1,7 +1,10 @@
 <h2>Switch Frontend</h2>
 
+<h3>After you submit, you will need to refresh manually to get your new frontend!</h3>
+
 <%= form_for @conn, Routes.frontend_switcher_path(@conn, :do_switch), fn f -> %>
   <%= select(f, :frontend, @choices) %>
 
   <%= submit do: "submit" %>
 <% end %>
+