filter custom post query by taxonomy

Hi i’m basically trying to edit the featured-product widget that comes with Woocommerce to filter results by the product category taxonomy.

Either by ID or by Slug.

I think this is the query that pulls the featured products, but i’m unable to find any documentation that could help me filter by categories.

<?php $query_args = array('posts_per_page' => $number, 'no_found_rows' => 1, 'post_status' => 'publish', 'post_type' => 'product' );

    $query_args['meta_query'] = array();

    $query_args['meta_query'][] = array(
        'key' => '_featured',
        'value' => 'yes'
    );
    $query_args['meta_query'][] = $woocommerce->query->stock_status_meta_query();
    $query_args['meta_query'][] = $woocommerce->query->visibility_meta_query();

    $r = new WP_Query($query_args);

    if ($r->have_posts()) : ?>

Any help would be amazing, thanks in advance