integrating block editor in my wordpress theme

Hi, i am making a new wordpress theme taking a template from underscores.me

So i am trying to add code snipper in function.php to get this block editor by default when i click customize my theme.

https://ibb.co/mqLVgmN

i added the code.

add_theme_support( 'editor-styles' );

function set_block_editor_by_default() {
    set_user_setting( 'editor', 'block' );
}
add_action( 'customize_controls_init', 'set_block_editor_by_default' );

but it does not open that block editor by default when i click customize the theme.

anyone can help?”