Add categories field to Fundraiser form

functions.php

<?php
add_filter( 'charitable_fundraiser_submission_campaign_fields', function( $fields, Charitable_Ambassadors_Fundraiser_Form $form ) {
	$parent_fields        = $form->get_sanitized_campaign_form_fields( 'campaign-details' );
	$fields['categories'] = $parent_fields['categories'];
	return $fields;
}, 10, 2 );