Crushes internal stylesheets.
npm install jeffkreeftmeijer/crush
cat input.html | crush
<html>
<head>
<style>body{font:22px/1.6 system-ui,sans-serif;margin:auto;max-width:35em;padding:0 1em}</style>
</head>
<body>
<h1>Hello world!</h1>
</body>
</html>