How to point “add_menu_page” to HTML file rather than PHP function

From the codex page:

$menu_slug
(string) (required) The slug name to refer to this menu by (should be unique for this menu). Prior to Version 3.0 this was called the file (or handle) parameter. If the function parameter is omitted, the menu_slug should be the PHP file that handles the display of the menu page content.
Default: None