JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.2/css/bootstrap.min.css">
<script src="//netdna.bootstrapcdn.com/bootstrap/3.0.2/js/bootstrap.min.js"></script>
<nav class="navbar navbar-default" role="navigation"> 
            <div class="container">
                <div class="navbar-header">
                <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-ex1-collapse">
                    <span class="sr-only">Toggle navigation</span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                </button>
                    <a class="navbar-brand" href="index.html">Welsh for Adults</a>
                </div>

                <div class="collapse navbar-collapse navbar-ex1-collapse">
                    <ul class="nav navbar-nav">
                        <li class="active"><a href="index.html"><span class="glyphicon glyphicon-home" style="font-size:85%;"></span> Home</a></li>
                        <li><a href="taster.html">Welsh Taster Course</a></li>
                        <li><a href="courses.html">Courses</a></li>
                        <li><a href="activities.html">Informal Learning Activities</a></li>
                    </ul>
                    <ul class="nav navbar-nav navbar-right">
                        <li><button type="button" class="btn btn-danger navbar-btn change-lang" data-lang="cym">Cymraeg</button></li>
                    </ul>
                </div>

            </div>
        </nav>

CSS

@media (min-width: 788px){
.container {
width: 100% !important;
}