show error when login is invalid

app/views/devise/sessions/new.html.erb

@@ -3,6 +3,10 @@
 </h2>
 
 <%= form_for(resource, as: resource_name, url: session_path(resource_name)) do |f| %>
+  <%- flash.each do |name, msg| -%>
+    <%= content_tag :div, msg, :id => "flash_#{name}" if msg.is_a?(String) %>
+  <%- end -%>
+
   <div class="my-3">
     <%= f.label :email %><br />
     <%= f.email_field :email, autofocus: true, autocomplete: "email", class: TailwindHelper.input_classes %>