BUTTON WITHIN THE INPUT FIELD
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<!DOCTYPE html>
<html lang="en">
<head>
  <title>Bootstrap </title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.1/dist/css/bootstrap.min.css" rel="stylesheet"> 
  <script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.9.2/dist/umd/popper.min.js" integrity="sha384-IQsoLXl5PILFhosVNubq5LC7Qb9DXgDA9i+tQ8Zj3iwWAwPtgFTxbJ8NT4GN1R8p" crossorigin="anonymous"></script>
  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.1/dist/js/bootstrap.min.js" integrity="sha384-Atwg2Pkwv9vp0ygtn1JAojH0nYbwNJLPhwyoVbhoPwBhjQPR5VtM2+xf0Uwh9KtT" crossorigin="anonymous"></script></head>
<body>
    <h2> Button at left of input field </h2>
	<div class="input-group mb-3">
	  <input type="file" class="form-control" id="inputGroupFile03" aria-describedby="inputGroupFileAddon03" aria-label="Upload">
	  <button class="btn btn-primary" type="button" id="inputGroupFileAddon03">Button</button>
	</div>
	
</body>
</html>