ckeditor/ckeditor5-engine

<style>
    .my-green-link {
        color: #209a25;
        border: 1px solid #209a25;
        border-radius: 2px;
        padding: 0 3px;
        box-shadow: 1px 1px 0 0 #209a25;
    }
</style>

<div id="snippet-link-classes">
    <p>All links in this <a href="https://ckeditor.com">editor</a> have a custom <code>.my-green-link</code>
    CSS <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/class">class</a> attribute.</p>
</div>