how to use glyphicon bootstrap 4 code example
Example 1: glyphicon cdn bootstrap 4
<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" type="text/css" rel="stylesheet">
Example 2: glyphicon-user bootstrap 4
<button type="button" class="btn btn-default navbar-btn">Sign in</button>