[WordPress] Replace WordPress logo on the page wp-login.php

functions.php

// custom admin login logo
function custom_login_logo() {
    echo '<style type="text/css">
    h1 a { background-image: url(' . get_stylesheet_directory_uri() . '/images/logo.png) !important; }
    </style>';
}
add_action('login_head', 'custom_login_logo');