Add WebSite mark-up on category pages

functions.php

<?php

add_filter( 'wp_head', function() {
  
	// Bail out if it's not a category.
	if ( ! is_category() ) {
		return;
	}
  
	// Check that the Wordlift_Jsonld_Service exists.
	if ( ! class_exists( 'Wordlift_Jsonld_Service' ) ) {
		echo '<!-- WordLift JSON-LD service not found. -->';

		return;
	}

	// Get the JSON-LD, $is_homepage = `true`.
	$jsonld = json_encode( Wordlift_Jsonld_Service::get_instance()->get_jsonld( true ) );

	// Finally print the JSON-LD out.
	?>
	<script type="application/ld+json"><?php echo $jsonld; ?></script>
	<?php
}, 10, 0 );