Create a simple HTML form with two input fields: one for the username and one for the password. Add a submit button to the form. The form should have the following behaviour:

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  - When the user clicks the submit button, if the username or password field is empty, an error message should be displayed below the respective field.


• - If both fields are filled, the form should display a message saying 'Form submitted successfully' below the submit button.


• - Use JavaScript to handle the form validation and display the messages.