WordPress: Check if a custom template exists in the theme folder, if not, then use the plugin template file

check-for-template.php

<?php
// The template
$template = 'my-custom-script.php';

// If a template file exists in the theme folder, use it.
if ( $theme_file = locate_template( array( 'my-custom-files/' .  $template ) ) ) {
	include(get_template_directory() . '/my-custom-files/' . $template);
} else { // Otherwise, use the plugin template file.
	include(plugin_dir_path( __FILE__ ) . '/templates/' . $template);
}
?>