Add Custom Link To WordPress Admin Dashboard

custom-dash-link.php

 add_action( 'admin_menu', 'linked_url' );
    function linked_url() {
    add_menu_page( 'linked_url', 'External link', 'read', 'my_slug', '', 'dashicons-text', 1 );
    }

    add_action( 'admin_menu' , 'linkedurl_function' );
    function linkedurl_function() {
    global $menu;
    $menu[1][2] = "http://www.example.com";
    }