font awesome category icon code example
Example: submenu icon font awesome
<div class="list-group">
<a class="list-group-item" href="#"><i class="fa fa-home fa-fw" aria-hidden="true"></i> Home</a>
<a class="list-group-item" href="#"><i class="fa fa-book fa-fw" aria-hidden="true"></i> Library</a>
<a class="list-group-item" href="#"><i class="fa fa-pencil fa-fw" aria-hidden="true"></i> Applications</a>
<a class="list-group-item" href="#"><i class="fa fa-cog fa-fw" aria-hidden="true"></i> Settings</a>
</div>