add demo alert

app/views/shared/_demo_alert.html.erb

@@ -0,0 +1,9 @@
+<div class="absolute top-0 w-full h-0">
+  <div class="max-w-xl mx-auto mt-1.5">
+    <div class="px-4 py-3 rounded-2xl flex items-center justify-between mx-4 md:mx-0">
+      <a target="_blank" href="<%= start_form_url(slug: ::Template.first&.slug) %>" class="font-medium w-full text-center underline">
+        Demo Environment
+      </a>
+    </div>
+  </div>
+</div>