app/views/design/layouts/application.html.erb
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<title><%= yield :title %> — Osuny</title>
<%= stylesheet_link_tag 'admin', media: 'all' %>
<%= favicon_link_tag 'favicon.png' %>
</head>
<body>
<nav class="navbar navbar-light">
<div class="container justify-content-center">
<a class="navbar-brand" href="/">
<%= image_tag 'osuny-black.svg',
class: 'img-fluid py-4',
alt: 'Osuny',
width: 100 %>
</a>
</div>
</nav>
<main class="container-fluid mt-5 pt-5">
<%= yield %>
</main>
</body>
</html>