add sso settings placeholder

app/views/sso_settings/index.html.erb

@@ -0,0 +1,8 @@
+<div class="flex flex-wrap space-y-4 md:flex-nowrap md:space-y-0">
+  <%= render 'shared/settings_nav' %>
+  <div class="flex-grow max-w-xl mx-auto">
+    <h1 class="text-4xl font-bold mb-4">SMS</h1>
+    <%= render 'placeholder' %>
+  </div>
+  <div class="w-0 md:w-52"></div>
+</div>