You can try this approach:

  1. Set ID attribute for your input element (eg: my_input)

  1. Add HTML element and insert the following code. Make sure that the ID attribute matches the one you have setup for the input element.
<script>
  var inputElement = document.getElementById("my_input");

  inputElement.addEventListener("input", function() {
    this.value = this.value.toUpperCase();
  });
</script>

The input value will be updated to uppercase as user types