add meta tag viewport

app/views/layouts/application.html.erb

@@ -5,6 +5,7 @@
     <%= favicon_link_tag 'icontitle.png' %>
     <%= csrf_meta_tags %>
     <%= csp_meta_tag %>
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <%= stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track': 'reload' %>
     <%= javascript_include_tag 'application', 'data-turbolinks-track': 'reload' %>
     <%= render 'shared/shim' %>