Add button to dismiss changeset locked notification in Customizer without taking over the lock from the other user

add-customize-changeset-locked-notification-dismiss-button.js

wp.customize.notifications.bind( 'add', function( notification ) {
	if ( 'changeset_locked' === notification.code ) {
		notification.render = (function( render ) {
			return function() {
				var li = render.call( notification ), button;
				button = jQuery( '<button type="button" class="button button-secondary">Dismiss</button>' );
				button.on( 'click', function() {
					notification.parent.remove( notification.code );
				} );
				li.find( '.action-buttons' ).append( button );
				return li;
			};
		})( notification.render );
	}
} );