Enable Featured Image (thumbnail) for WP Job Manager Resumes

functions.php

<?php

add_filter( 'register_post_type_resume', 'register_post_type_resume_enable_featured_image' );
// Unfortunately all reusme uploads must be attached (added to media library) to support featured image
add_filter( 'resume_manager_attach_uploaded_files', '__return_true' );

function register_post_type_resume_enable_featured_image( $post_type ) {
	if( ! in_array( 'thumbnail', $post_type['supports'] ) ){
		$post_type['supports'][] = 'thumbnail';
	}
	return $post_type;
}