JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>Первый</li>
    <li>Второй</li>
</ul>

CSS

ul {
    margin: 0;
    padding: 0;
}
li {
    display: inline-block;
    padding: 5px 10px;
}

li:first-child {
    border-right: 1px solid #ccc;
    
}