Kirki: generate toggles for each taxonomy term

You can use a Kirki helper class for this (pass your taxonomy into Kirki_Helper::get_terms), but you need to register after the taxonomies are registered, otherwise you get an error:

function my_theme_add_categories_customizer_control() {
Kirki::add_field('my_config', array(
    'type' => 'multicheck',
    'settings' => 'show_months',
    'label' => esc_attr__('My Control', 'my_textdomain'),
    'section' => 'months',
    'priority' => 10,
    'choices' => Kirki_Helper::get_terms(array('months'))
));
}

add_action( 'init', 'my_theme_add_categories_customizer_control', 12 );