feat: allow opt-out of define()

[andreruffert]

What changed (additional context)

Introduce option to opt-out of define() by adding a ?define=false query parameter to the import/script URL.

• Allows the use of a different tag name
• Run some additional configuration before definition etc.

<script type="module">
  // <progressive-image> is not automatically defined
  import "progressive-image-element?define=false";

  // ...

  ProgressiveImageElement.define("different-tag-name");
</script>