Enqueue external styles in child themes

functions.php

<?php 
// enqueue styles for child theme
function example_enqueue_styles() {
	
	// enqueue parent styles
	// Add style.css inside the /assets/css/ directory.
	wp_enqueue_style('parent-theme', get_template_directory_uri() .'/assets/css/style.css');
	
}
add_action('wp_enqueue_scripts', 'example_enqueue_styles');