How to add A <fieldset> element located outside a form (but still a part of the form)

Fieldset Example.

index.html

Example: HTML

 <form action="/action_page.php" method="get" id="form1">
  What is your favorite color? <input type="text" name="fav_color"><br>
  <input type="submit">
</form>

<fieldset form="form1">
  Name: <input type="text" name="username"><br>
  Email: <input type="text" name="usermail"><br>
</fieldset>

Output should be:

Type:	html
Category:	Web Tutorial
Sub Category:	HTML Attribute
Uploaded by:	Admin