Add support for readonly fields?

[Scyntherei]

I have come across an issue where I need a field to contain a static value and be read only. Ideally the label would still appear and stick to the far right to inform users what the field is representing.

<ul class="form-list">
    <li>
        <label for="username" class="standard-form-label">Username</label>
        <input type="text" name="username" id="username" class="standard-form-field" placeholder="Username" value="<?php echo $username; ?>" readonly="readonly">
    </li>
</ul>

If there is an easy solution to this, it might be worth adding to the demo or documentation.