Append Site Options to WP JSON API Index

append_site_options_to_wp_json_index.php

<?php
//https://developer.wordpress.org/reference/hooks/rest_index/
add_filter( 'rest_index', 'append_site_public_settings_to_rest_api_index', 10, 2 );

function append_site_public_settings_to_rest_api_index( $response, $request ){
	$options_to_include = array(
		'date_format',
		'time_format',
		'gmt_offset',
		'blog_public',
		'tag_base',
		'wp_page_for_privacy_policy',
		'posts_per_page',
		'permalink_structure',
		'template',
		'stylesheet'
	);
	
	$options = wp_load_alloptions();;
	$fields_to_add = array_intersect_key( $options, array_flip( $options_to_include ) );
	$response->data = array_merge( $response->data, $fields_to_add );
	return $response;
}
?>