contact_form_sc.php

<?php

function bs_contact_form_sc($atts, $content = null) {
	$attributes = [
		'name-placeholder' => 'Name',
		'email-placeholder' => 'Email'
	];
  
  $at = shortcode_atts( $attributes , $atts );

  ob_start();
?>

<div 
	class="contact-form" 
	data-props='{
		"placeholders": {
			"name": "<?php echo $at['name-placeholder']; ?>",
			"email": "<?php echo $at['email-placeholder']; ?>"
		}
	}'
>
</div>

<?php

  return ob_get_clean();
}

add_shortcode( 'bs_contact_form', 'bs_contact_form_sc' );