I have a simple bootstrap 4 menu and would like to expand the submenu by default for mobile users. How would I accomplish this (first preference is for a CSS only solution)?
<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
<a class="navbar-brand" href="http://www.mywebsite.com"> <img src="https://www.mywebsite.com/logo.png" style="width:75px;"> My Website</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto">
<li class="nav-item active">
<a class="nav-link" href="~/">Home <span class="sr-only">(current)</span></a>
</li>
<!-- expand this menu by default for mobile users -->
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
sub menu
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="~/Page 1">Page 1</a>
<a class="dropdown-item" href="~/Page 2">Page 2</a>
<a class="dropdown-item" href="~/Page 3">Page 3</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="~/Page 4">Page 4</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Page 5</a>
</li>
</ul>
</div>
