JSFiddle - React, Tailwind, and code Playground

HTML

<!doctype html>
<div id="host"></div>
<script>
  document.getElementById("host").attachShadow({ mode: "open" }).innerHTML = `
    <style>
      ::slotted(span) {
        color: blue;
      }
    </style>
    <slot>
      <span>Does this match ::slotted? Per spec, it seems it should!</span>
    </slot>
  `;
</script>