test-repo/changelog_unreleased/html/19709.md

Fix attribute name normalization (#19709 by @fisker)

<!-- Input -->
<span CLASS="foo"></span>
<div CLASS="foo"></div>

<!-- Prettier stable -->
<span CLASS="foo"></span>
<div class="foo"></div>

<!-- Prettier main -->
<span class="foo"></span>
<div class="foo"></div>