facetwp search placeholder

<?php

add_filter( 'facetwp_facet_render_args', function( $args) {
	if ( 'my_search_facet' == $args['facet']['name'] ) {  // change my_search_facet to name of your facet
		$args['facet']['placeholder'] = 'Something';
	}
	return $args;
} );